Plate Motion Evidence - Middle School Earth and Space Science

What boundary type is indicated by earthquakes along a fault but little or no volcanism?

Transform boundary. Plates slide past each other without creating/destroying crust.
Which force pulls an oceanic plate into the mantle and helps drive plate motion at subduction zones?

Slab pull. Gravity pulls dense subducting slabs down into mantle.
What is the main driving mechanism that moves tectonic plates over time?

Convection currents in Earth's mantle. Hot mantle material rises and falls, dragging plates along.
What seafloor observation shows that oceanic crust gets older with distance from a ridge?

Rock ages increase as you move away from the mid-ocean ridge. New crust forms at ridges, so older rocks are found farther away.
What magnetic pattern on the seafloor provides evidence for seafloor spreading?

Symmetrical magnetic "stripes" on both sides of ridges. Earth's magnetic reversals recorded in cooling lava create mirror patterns.
What feature on the ocean floor is the key location where new crust forms?

Mid-ocean ridge. Underwater mountain chain where magma creates new oceanic crust.
Which feature most strongly indicates an oceanic-oceanic convergent boundary?

Volcanic island arc. Forms when oceanic plate subducts beneath another oceanic plate.
Identify the boundary type at a mid-ocean ridge.

Divergent plate boundary. Plates move apart, creating new oceanic crust between them.
Identify the likely boundary: a linear chain of volcanoes grows older away from the active volcano.

Plate moving over a hotspot (hotspot track). Fixed mantle plume creates progressively older volcanoes in plate motion direction.
Which boundary is indicated by new basalt, high heat flow, and shallow earthquakes at a ridge axis?

Divergent plate boundary. All features indicate active seafloor spreading at mid-ocean ridge.
What is a divergent plate boundary?

A boundary where two plates move apart. Plates separate, creating new crust at spreading centers.
What is a transform plate boundary?

A boundary where plates slide past each other. Lateral motion causes earthquakes without creating/destroying crust.
What is the name of the supercontinent supported by fossil, rock, and coastline evidence?

Pangaea. All continents joined ~250 million years ago.
Which statement correctly links evidence to motion: why are magnetic stripes mirrored across a ridge?

New crust forms at the ridge and spreads outward equally on both sides. Simultaneous formation records same magnetic orientation.
What does matching rock layers and mountain belts across oceans indicate?

Continents were once connected before plate motion separated them. Same rock types and ages span ocean-separated continents.
Which seafloor feature is the main evidence that new ocean crust forms at divergent boundaries?

Mid-ocean ridge. New oceanic crust forms at ridges as plates diverge.
What is seafloor spreading evidence shown by the age of ocean crust away from mid-ocean ridges?

Ocean crust gets older with distance from the ridge. Dating shows youngest rocks at ridge, oldest at edges, proving spreading.
Identify the boundary: the oldest ocean crust is farthest from the mid-ocean ridge.

Divergent boundary (seafloor spreading). Age increases with distance from ridge where new crust forms.
What is the most direct modern measurement that plates move today, in centimeters per year?

GPS measurements. Satellites track precise plate positions, showing 2-10 cm/year movement rates.
Which fossil evidence supports that continents were once joined?

Same fossils found on now-separated continents. Organisms couldn't cross oceans, proving continents were connected.
What pattern in ocean-floor rock ages provides evidence for seafloor spreading?

Youngest rocks at ridges, older rocks farther away. Age increases with distance from spreading center.
Identify the boundary type: two plates move apart and magma rises to form new crust.

Divergent boundary. New crust forms as plates separate at ridges.
What evidence from the ocean floor shows that plates move apart at mid-ocean ridges?

Symmetrical magnetic stripes on both sides of the ridge. Alternating normal/reversed polarity records seafloor spreading history.
What rock-structure evidence supports continental drift across now-separated continents?

Matching mountain belts and rock layers across different continents. Continuous geological features prove continents were once joined together.
Which evidence best supports hotspot motion of a plate: a chain of islands with ages increasing away from one end?

Hotspot track: older islands farther from the active volcano. Plate moves over stationary magma source, creating age progression.
Which boundary type is indicated by frequent shallow earthquakes but little volcanism?

Transform plate boundary. Plates slide past each other without creating or destroying crust.
Identify the plate motion indicated by a hotspot chain where island ages increase away from the active volcano.

A plate moving over a relatively stationary mantle hotspot. Stationary hotspot creates volcanic islands as plate moves over it.
Identify the plate-motion evidence: a volcanic island chain gets older away from one end.

Hotspot track; plate moved away from the active hotspot. Age progression shows direction and rate of plate movement.
What landform commonly forms above an oceanic-continental subduction zone?

Volcanic mountain chain (continental volcanic arc). Subducting plate melts, creating magma that rises to form volcanoes.
Which force is most associated with pulling a plate into the mantle at subduction zones?

Slab pull. Dense oceanic lithosphere sinks, pulling attached plate toward subduction zone.
What climate evidence shows continents have moved over time?

Glacial deposits and coal beds found in unexpected climates. Tropical fossils in polar regions prove latitude changes.
What is the most accepted driving mechanism that explains how plates move over time?

Mantle convection transferring heat and causing flow. Hot mantle rises and cool mantle sinks, dragging plates.
What is seafloor spreading?

Creation of new oceanic crust at mid-ocean ridges. Magma rises at ridges, solidifies, and pushes older crust outward.
What is the definition of a tectonic plate in plate tectonics?

A rigid slab of lithosphere that moves over the asthenosphere. Plates are solid rock layers that float and move on the plastic mantle below.
Which boundary type is most strongly associated with deep ocean trenches and subduction?

Convergent boundary. Subducting plates create deep trenches where they bend downward.
Which plate boundary type is identified by deep earthquakes and a subducting slab?

Convergent boundary with subduction. Oceanic plate bends downward into mantle, creating deep earthquake zones.
What is the main evidence that transform boundaries involve plates sliding past each other?

Frequent shallow earthquakes with little or no volcanism. Plates grind past each other causing quakes but no melting/volcanoes.
What is a hotspot track, and what does it show about plate motion over time?

A chain of volcanoes recording plate movement over a hotspot. Stationary magma source creates age-progressive volcanic islands as plate moves.
What is paleomagnetism in rocks used to infer about plate motion?

Past magnetic field direction and plate movement over time. Magnetic minerals record field direction when rocks form, showing plate positions.
Which observation about ocean-floor rock ages supports seafloor spreading from ridges?

Youngest rocks at ridges; older rocks farther away. Age increases symmetrically away from ridge axis, proving continuous crust formation.
What direct measurement method provides current plate motion rates and directions?

GPS measurements of plate movement. Satellites track precise positions showing plates move cm/year.
What does the global pattern of earthquakes and volcanoes along plate edges show?

Plate boundaries are where plates interact and move. Most geological activity occurs at plate edges.
What climate evidence supports continental drift between different latitudes?

Glacial deposits/striations in now-warm regions. Ice sheets existed when continents were at different latitudes.
Which force pushes plates away from a mid-ocean ridge due to elevated ridge topography?

Ridge push. Gravity slides plates down from elevated ridge crests.
What causes magnetic stripes to form in oceanic crust?

Iron-bearing basalt records Earth's magnetic field as it cools. Minerals align with magnetic field when lava solidifies.
What type of boundary forms when two plates move toward each other?

Convergent plate boundary. Plates collide at convergent boundaries, often forming mountains.
What is a hotspot track used as evidence for plate motion over time?

A chain of volcanoes recording plate motion over a hotspot. Stationary magma source creates volcanoes as plate moves over it.
What does an increasing earthquake depth inland from a trench indicate about plate motion?

A subducting slab dipping into the mantle. Deeper earthquakes trace the descending plate's path.
Which plate boundary type is identified by shallow earthquakes and plates sliding past each other?

Transform boundary. Lateral motion without creation or destruction of crust, like San Andreas Fault.
What climate evidence supports plate motion when glacial scratches are found in now-warm regions?

Ancient glacial evidence in unexpected climates. Shows continents moved from polar to tropical regions.
What is mantle convection in the context of tectonic plate movement?

Hot mantle rises, cool mantle sinks, creating circulating flow. Temperature differences cause density variations that drive circular flow.
What fossil evidence supports that continents were once joined into a larger landmass?

Same land fossils found on continents now separated by oceans. Identical species couldn't cross oceans, proving past connections.
What is the main physical layer that tectonic plates are part of and move with?

The lithosphere (crust plus uppermost mantle). Rigid outer shell that moves as solid units over the softer layer below.
What magnetic pattern on the seafloor shows seafloor spreading over time?

Symmetric magnetic stripes on both sides of ridges. Mirror pattern proves spreading from central ridge.
What type of boundary forms when two plates slide horizontally past each other?

Transform plate boundary. Plates grind past each other horizontally at transform boundaries.
What tool provides direct measurements of present-day plate motion rates and directions?

GPS satellite measurements. Tracks precise plate positions over time to calculate motion.
Which statement is supported by rock-age evidence: crust is youngest at ridges or at trenches?

Crust is youngest at mid-ocean ridges. Dating shows new crust forms at spreading ridges, not subduction trenches.
What does a deepening line of earthquakes beneath a continent indicate?

A subducting plate forming a Wadati–Benioff zone. Earthquakes deepen as the oceanic plate descends into the mantle.
What is the evidence from seafloor rock ages that supports seafloor spreading?

Youngest rocks at ridge; older rocks farther away. Proves new crust forms at ridge and spreads outward.
Identify the boundary type: Two continents collide and form a high mountain range with no trench.

Convergent boundary (continental-continental collision). Neither plate subducts; crust crumples upward instead.
Which boundary type most directly produces frequent shallow earthquakes with little volcanism?

Transform boundary. Plates grind horizontally past each other without subduction.
What is the softer layer beneath the lithosphere that plates move over?

The asthenosphere (plastic upper mantle). Partially molten layer allows lithospheric plates to slide and move.
What force helps pull a subducting plate into the mantle, increasing plate motion?

Slab pull. Weight of descending slab pulls rest of plate along.
Which plate boundary type is supported by evidence of frequent shallow earthquakes but little volcanism?

Transform boundary. Plates slide horizontally past each other without creating/destroying crust.
What magnetic pattern on the seafloor is evidence for seafloor spreading?

Symmetric magnetic polarity stripes on both sides of ridges. Earth's magnetic field reversals create alternating bands as new crust forms.
Which seafloor feature is strong evidence that subduction is occurring at a convergent boundary?

Deep-ocean trench. Trenches form where oceanic plates subduct into the mantle.
Which evidence best indicates the direction of seafloor spreading at a mid-ocean ridge?

Magnetic stripes mirror outward from the ridge on both sides. Symmetric pattern shows crust spreads equally in both directions.
What is subduction?

One plate sinks beneath another into the mantle. Denser plate descends, recycling crust back into mantle.
What is Pangaea?

An ancient supercontinent that later broke apart. All continents were joined ~250 million years ago before drifting apart.
Which boundary type is indicated by two continents colliding and forming very high mountains with little volcanism?

Convergent boundary (continent-continent collision). Neither plate subducts, crust thickens upward instead.
Which plate is denser and more likely to subduct at a convergent boundary: oceanic or continental?

Oceanic plate. Oceanic crust is made of dense basalt, while continental crust is lighter granite.
Which boundary type is identified by rift valleys on continents and mid-ocean ridges in oceans?

Divergent boundary. Plates separate, creating new crust through volcanic activity.
What landform is most directly created where oceanic crust subducts beneath continental crust?

A volcanic mountain chain along the continent. Subducting plate melts, creating magma that rises to form volcanoes.
Identify the evidence type: identical plant fossils are found in South America and Africa.

Fossil correlation evidence for continental drift. Organisms couldn't cross ocean; shows continents were once connected.
What is a divergent plate boundary?

A boundary where plates move apart. Creates new crust as plates separate, like at mid-ocean ridges.
What is the best definition of a tectonic plate in plate tectonics?

A rigid lithosphere slab moving over the asthenosphere. The lithosphere floats and moves on the plastic asthenosphere below.
What is a convergent plate boundary?

A boundary where two plates move toward each other. Plates collide, causing subduction, mountains, or compression.
Which seafloor feature is the main location where new ocean crust forms?

Mid-ocean ridge. Underwater mountain chain where plates diverge.
What type of fossil evidence supports past plate connections when identical fossils occur on separated continents?

Matching fossils across continents. Same species couldn't cross oceans, proving past connections.
Which plate boundary type is identified by seafloor spreading at mid-ocean ridges?

Divergent boundary. Plates separate at ridges where new oceanic crust continuously forms.
Which plate boundary type is identified by trenches and volcanic arcs?

Convergent boundary with subduction. Oceanic plates sink beneath others, creating deep trenches and volcanic chains.
Which seafloor feature provides direct evidence for divergent plate motion in the oceans?

Mid-ocean ridge. Long underwater mountain chain where plates spread apart.
Which boundary type most commonly produces frequent shallow earthquakes but little volcanism?

Transform boundary. Sliding motion releases energy as earthquakes without melting rock.
Which fossil evidence supports continental drift across now-separated continents?

Same fossils found on continents now far apart. Identical species couldn't cross oceans, proving continents moved.
What feature most commonly forms where one oceanic plate subducts under another?

A volcanic island arc. Subducting oceanic plate creates magma that forms island volcanoes.
Identify the plate-boundary type: two plates move apart and new basalt forms between them.

Divergent boundary. New basalt forms where plates separate, characteristic of spreading centers.
What is the modern theory that explains plate movement using mantle processes and plate interactions?

Plate tectonics. Explains plate motion through convection currents and lithosphere-asthenosphere interactions.
Which measurement tool provides direct evidence of present-day plate motion rates and directions?

GPS satellite measurements. GPS tracks plate movement in real-time with precision.
Choose the best evidence for seafloor spreading: magnetic stripes, monsoons, or soil layers?

Magnetic stripes. Magnetic reversals recorded in basalt prove new crust forms at ridges.
What paleoclimate evidence indicates continents changed latitude over time?

Glacial deposits and striations found in present-day warm regions. Ancient ice evidence in tropical areas shows continents moved from polar regions.
What is subduction in plate tectonics?

One plate sinks beneath another into the mantle. Denser oceanic plate descends beneath another plate.
What type of fossil evidence supports past connections between now-separated continents?

Same land fossils found on different continents. Identical species couldn't cross oceans, proving continents were once connected.
What do matching rock layers and mountain belts on different continents suggest about past plate motion?

Continents were once joined and later moved apart. Matching geology across oceans proves continents drifted apart.
Which process best explains why oceanic crust is generally younger than continental crust?

Oceanic crust is created at ridges and destroyed at subduction zones. Continuous recycling keeps oceanic crust young; continental crust isn't subducted.
What is the evidence from earthquake locations that outlines plate boundaries?

Earthquakes cluster in narrow belts along boundaries. Most earthquakes occur where plates interact and stress builds.
What does a Wadati–Benioff zone (deepening earthquake pattern) indicate?

An oceanic plate is subducting beneath another plate. Earthquake depths increase as the slab descends into the mantle.
Which ocean-floor feature most directly marks where old crust is recycled into the mantle?

Deep-ocean trench at a subduction zone. Deepest parts of ocean where oceanic plates sink back into mantle.
What does the close fit of continental coastlines (for example, Africa and South America) support?

Continental drift from a former joined landmass. Coastlines match like puzzle pieces when reassembled.
Which evidence best supports seafloor spreading: symmetric magnetic stripes or matching fossils?

Symmetric magnetic stripes. Magnetic reversals recorded in ocean crust directly prove seafloor spreading.
Which boundary is indicated by a line of volcanoes parallel to a deep-ocean trench?

Convergent boundary with subduction. Subducting oceanic plate creates both trench and volcanic arc.
Which hotspot evidence indicates the direction of plate motion: younger-to-older volcano ages along a chain?

The plate moves from the youngest volcano toward the older ones. Plate motion direction is opposite to the age progression along the chain.
Which age pattern of oceanic crust supports seafloor spreading?

Youngest at ridges; progressively older away from ridges. New crust forms at ridges and moves outward, aging with distance.
Identify the boundary type: plates slide sideways, causing frequent shallow earthquakes.

Transform boundary. Friction from sliding causes earthquakes, no volcanoes.
Identify the boundary type: new ocean crust forms, and seafloor ages increase away from the center.

Divergent boundary (mid-ocean ridge). Spreading centers create new crust with age increasing symmetrically outward.
What seafloor feature forms where two plates move apart at a divergent boundary in the ocean?

A mid-ocean ridge (new basaltic crust forms there). Magma rises where plates separate, creating new oceanic lithosphere.
What does the global pattern of earthquakes along plate boundaries indicate about plate motion?

Plates interact at boundaries where most earthquakes occur. Earthquakes concentrate where plates meet and interact, outlining boundaries.
What is subduction?

One plate sinks beneath another into the mantle. Denser plate descends into mantle at convergent boundaries.
What is a transform plate boundary?

A boundary where two plates slide past each other. Lateral motion causes friction and earthquakes without creating/destroying crust.
Which boundary type best matches this evidence: a linear belt of shallow earthquakes with offset ridges?

Transform boundary. Offset ridges indicate lateral motion characteristic of transforms.
What does a chain of volcanic islands with increasing age away from one end indicate?

Plate motion over a stationary hotspot. The plate carries islands away from the hotspot, creating an age progression.
Identify the boundary type: two plates collide and form high mountain ranges without subduction.

Continent-continent convergent boundary. Equal-density plates crumple upward instead of one subducting.
What does the symmetry of magnetic stripes across a mid-ocean ridge indicate?

New crust forms at the ridge and moves outward equally. Matching patterns prove seafloor spreads symmetrically from the ridge center.
Which seafloor evidence shows ocean crust becomes older away from a mid-ocean ridge?

Increasing age of seafloor rocks with distance from the ridge. Radiometric dating shows youngest rocks at ridge, oldest far away.
What is a convergent plate boundary?

A boundary where plates move toward each other. Collision zones create mountains, trenches, or volcanoes.
What magnetic pattern in ocean crust supports seafloor spreading?

Symmetric magnetic polarity stripes on both sides of ridges. Mirror pattern proves crust spreads equally from central ridge.
Which boundary type most commonly forms deep-ocean trenches and volcanic arcs?

Convergent boundary with subduction. Denser oceanic plate sinks beneath lighter plate.
What is the direct evidence used today to measure plate motion over years to decades?

GPS measurements of plate movement. Satellites track precise plate positions over time.
Which boundary type best matches this evidence: a mid-ocean ridge with the youngest basalt at the center?

Divergent boundary. Young basalt at center indicates active seafloor spreading.
What is a hot spot, as used as evidence for plate motion over time?

A long-lived mantle plume that forms volcanoes through a moving plate. Stationary heat source melts through crust as plate moves over it.
Identify the boundary type: plates slide past each other, producing many shallow earthquakes.

Transform boundary. Lateral motion causes friction and earthquake release.
What major evidence shows plate boundaries by the global distribution of earthquakes and volcanoes?

Earthquakes and volcanoes cluster in narrow belts. Most seismic and volcanic activity occurs along plate edges, not randomly.
What seafloor feature provides evidence of seafloor spreading at divergent boundaries?

Mid-ocean ridge. Underwater mountain chain where new oceanic crust forms and spreads outward.
What causes the magnetic stripes recorded in basalt on the seafloor?

Earth magnetic field reversals during new crust formation. Basalt records magnetic direction when cooling from magma.
What is seafloor spreading?

Formation of new ocean crust at mid-ocean ridges. Magma rises at ridges, solidifies, and pushes older crust outward.
Which boundary type is identified by plates sliding past and frequent shallow earthquakes?

Transform boundary. Lateral motion without creation or destruction of crust.
What pattern of magnetic stripes on the seafloor supports plate motion over time?

Symmetrical alternating polarity bands on both sides of ridges. Magnetic reversals create mirror-image patterns as crust spreads.
What does symmetrical magnetic striping on both sides of a mid-ocean ridge indicate?

New crust formed and moved outward during reversals. Earth's magnetic field reversals recorded in ocean crust.
Which GPS observation is direct evidence that plates move today?

Measured changes in position of points on Earth's surface over time. GPS satellites track plate movement of centimeters per year.
What fossil evidence best supports that South America and Africa were once connected?

Same land fossils found on both continents (for example, Mesosaurus). Freshwater reptile couldn't cross ocean, proving continents were once joined.
Which evidence shows plate direction using a hot spot: volcano ages increase toward or away from the active volcano?

Ages increase away from the active volcano. Plate moves over stationary hot spot, aging volcanoes.
Identify the boundary type: seafloor is created as magma rises and solidifies at a ridge.

Divergent boundary (mid-ocean ridge). Upwelling magma creates new oceanic crust as plates separate.
What evidence pattern of earthquakes indicates a subducting slab?

Earthquakes increase in depth inland from a trench. Descending plate creates deeper quakes as it sinks into mantle.
Which boundary type is indicated by a deep-ocean trench next to a volcanic arc?

Convergent boundary with subduction. Oceanic plate sinks beneath another, creating trenches and volcanic arcs.
Which option best matches the evidence: shallow quakes in a straight line + no volcanoes?

Transform boundary. Plates slide horizontally past each other without creating/destroying crust.
Identify the boundary: seafloor shows mirror-image magnetic stripes across a ridge.

Divergent boundary. Magnetic reversals create symmetrical patterns at spreading centers.
Which plate boundary type is identified by plates sliding past each other with frequent earthquakes?

Transform boundary. Horizontal motion without creation or destruction causes shallow quakes.
Identify the boundary type: a long fault zone with shallow earthquakes and little volcanism.

Transform boundary. Lateral sliding produces earthquakes without creating or destroying crust.
What is the main mechanism that moves tectonic plates over time?

Mantle convection driven by Earth's internal heat. Hot material rises and cool material sinks, creating circular currents that drag plates.
Identify the evidence: matching coastline shapes plus identical fossils on both sides of an ocean. What conclusion follows?

The continents were once connected and later drifted apart. Multiple evidence types support Wegener's continental drift hypothesis.
Which option best matches the evidence: shallow quakes + ridge + youngest crust at center?

Divergent boundary (seafloor spreading). All three features indicate plates moving apart at ocean ridge.
What causes the magnetic stripes recorded in oceanic crust to alternate over time?

Geomagnetic polarity reversals. Earth's magnetic field flips periodically, recording direction in cooling basalt.
Which feature most strongly indicates an oceanic-continental convergent boundary?

Continental volcanic mountain chain near a trench. Subducting oceanic plate melts, creating continental volcanoes.
What pattern of seafloor ages is expected as you move away from a mid-ocean ridge?

Crust gets progressively older with distance from the ridge. New crust forms at ridge; older crust pushed farther away over time.
Which option best matches the evidence: trench + volcanic arc + quakes that deepen inland?

Convergent boundary with subduction. Classic subduction zone features where oceanic plate descends.
Which boundary type is indicated by a mid-ocean ridge and seafloor spreading?

Divergent plate boundary. Plates move apart at ridges where new oceanic crust forms.
Which boundary type most commonly forms mid-ocean ridges?

Divergent boundary. Spreading centers create new oceanic crust at underwater ridges.
What evidence from the ocean floor shows seafloor spreading at mid-ocean ridges?

Youngest crust at ridge; older crust farther away on both sides. Age increases symmetrically from the ridge center outward.
Which boundary type most directly forms mid-ocean ridges and new crust?

Divergent boundary. Spreading centers create new oceanic crust as plates separate.
Choose the best evidence for divergence: symmetric magnetic stripes + youngest crust at center. What process is indicated?

Seafloor spreading at a mid-ocean ridge. Classic evidence pattern for new crust formation at divergent plate boundaries.
What is the best evidence that continents were once connected, based on rock and mountain belts?

Matching rock types and mountain ranges across oceans. Continuous geological features split by ocean formation.
What is the name of the supercontinent used as evidence for large-scale plate motion?

Pangaea. All continents joined ~250 million years ago before breaking apart.
What landform most directly indicates a divergent boundary on continents?

A rift valley. Plates pulling apart create valleys as the crust stretches and drops.
What pattern in seafloor rock ages supports seafloor spreading?

Youngest rocks at ridges; older rocks farther away. New crust forms at ridges and moves outward, aging with distance.
What surface feature most commonly forms where oceanic crust subducts under a continent?

A volcanic mountain chain (continental volcanic arc). Subducting plate melts, creating magma that rises to form volcanoes.
Which rock property records Earth's magnetic field and helps date seafloor crust?

Magnetism in iron-bearing minerals (paleomagnetism). Minerals align with magnetic field when rock cools, preserving direction.
What climate evidence supports continental drift across different latitudes over time?

Glacial scratches and deposits in now-warm regions. Ancient ice sheets left marks in tropical areas, showing continents moved.
Identify the boundary type: plates slide past each other and offset streams or roads.

Transform boundary. Lateral motion causes surface features to be displaced horizontally.
Which evidence best supports that continents were once joined as a single landmass?

Matching fossils, rocks, and coastlines across oceans. Similar features on different continents show they were once connected.
What evidence along a deep-ocean trench indicates one plate is subducting beneath another?

A line of earthquakes that increases in depth inland. Descending plate bends and cracks at increasing depths as it sinks.
What is the name of the process that creates new oceanic crust at ridges?

Seafloor spreading. Magma rises at ridges, solidifies, and pushes older crust outward.
What is the primary mechanism that moves tectonic plates over time?

Mantle convection driven by Earth's internal heat. Hot mantle rises and cools in circular cells, dragging plates along.
Identify the evidence from earthquake locations that outlines plate boundaries globally.

Earthquakes cluster in narrow belts along boundaries. Most earthquakes occur at plate edges, mapping their locations.
What seafloor feature is strong evidence of a subduction zone?

Deep-ocean trench. Forms where subducting plate bends downward into mantle.
Identify the plate-boundary type: plates slide past each other and earthquakes are shallow.

Transform boundary. Lateral sliding with shallow earthquakes characterizes transform faults.
What seafloor feature provides evidence of seafloor spreading at divergent boundaries?

Mid-ocean ridges where new crust forms. Magma rises and solidifies, pushing older crust outward.
What boundary type is most associated with frequent shallow earthquakes but little volcanism?

Transform boundary. Plates slide horizontally past each other without creating or destroying crust.
What magnetic evidence on the seafloor supports plate motion over time?

Symmetric magnetic polarity stripes on both ridge sides. Magnetic reversals create mirror patterns as new crust forms.
What does a volcanic arc parallel to an ocean trench indicate about plate movement?

Subduction is occurring and magma rises above the sinking slab. Water from the sinking plate causes melting, creating arc volcanoes.
What is the primary evidence that plates move, based on volcano locations?

Volcanoes cluster along plate boundaries and hotspots. Volcanic activity concentrated where plates interact.
What type of evidence is provided by matching fossils on continents now separated by oceans?

Continents were once connected and later drifted apart. Same species couldn't cross oceans, proving land was connected.
What is the main driving force that moves tectonic plates over time?

Convection currents in Earth's mantle. Hot material rises and cool material sinks, creating circular flow that drags plates.
Identify the boundary type: an oceanic plate sinks, forming a trench and a volcanic arc.

Convergent boundary (subduction zone). Descending plate melts, creating arc volcanoes above.
Which boundary is indicated when two continental plates collide and form a high mountain range with little volcanism?

Convergent boundary (continental-continental collision). Continental crust is too buoyant to subduct, so it crumples upward.
What evidence from the Atlantic Ocean seafloor shows plates move apart over time?

Symmetric magnetic stripes on both sides of the Mid-Atlantic Ridge. Magnetic reversals create mirror-image patterns as new crust forms at ridges.
What is a convergent plate boundary?

A boundary where plates move toward each other. Causes collision, subduction, or mountain building.
Which type of crust is denser and more likely to subduct: oceanic or continental?

Oceanic crust. Higher density from basaltic composition makes it sink beneath continents.
What evidence from the ocean floor shows plates move away from mid-ocean ridges?

Symmetric magnetic stripes on both sides of the ridge. Reversals in Earth's magnetic field create mirror-image patterns.
Which climate evidence on a continent best supports that it moved from a different latitude?

Glacial deposits/striations in now-warm regions. Ancient ice evidence shows continents moved from polar regions.
What is the main process that moves tectonic plates over time in plate tectonic theory?

Convection in Earth's mantle (asthenosphere) drives plate motion. Hot material rises and cool material sinks, creating circular flow that moves plates.
What causes the alternating magnetic polarity recorded in oceanic basalt?

Periodic reversals of Earth's magnetic field during lava cooling. Iron minerals align with Earth's field when lava solidifies.
What past-climate evidence supports continental drift when found in now-warm regions?

Glacial deposits and striations in tropical areas. Ancient ice sheets couldn't form at current tropical latitudes without drift.
What is seafloor spreading?

New ocean crust forms at mid-ocean ridges. Magma rises and solidifies, pushing plates apart.
Which GPS observation provides direct evidence that plates move today?

Measured changes in distance between stations over time. GPS precisely tracks plate movement of centimeters per year.
What rock evidence supports past continental connections across oceans?

Matching rock types and mountain belts on different continents. Continuous geological features split by ocean formation.
Which direction is a plate moving if hotspot volcanoes get older to the northwest?

Northwest. Plate moves northwest over the fixed hotspot, leaving older volcanoes behind.
What driving force pushes plates away from a mid-ocean ridge due to elevated ridge topography?

Ridge push. Gravity on elevated ridge flanks creates outward force on plates.
Identify the boundary type: A chain of volcanic islands forms above a subducting oceanic plate.

Convergent boundary (oceanic-oceanic subduction). Subducting plate melts, creating magma that forms island arcs.
What rock evidence supports that continents were once joined and later separated?

Matching rock layers and mountain belts across oceans. Identical formations split by oceans show continents were once united.
Which plate type is more likely to subduct at a convergent boundary, oceanic or continental?

Oceanic plate. Denser oceanic crust sinks beneath lighter continental crust.
Which evidence pattern best indicates a subduction zone: shallow quakes only or quakes increasing in depth inland?

Earthquakes increasing in depth inland. Descending plate causes deeper quakes as it sinks.
Identify the boundary type: Ocean crust is youngest at the center and older outward in both directions.

Divergent boundary (mid-ocean ridge spreading). Age pattern proves new crust forms at ridge and spreads outward.
What is the main evidence that continents were once connected, based on matching shorelines?

Continental coastlines fit together like puzzle pieces. Wegener noticed coastlines match when continents are reassembled.
Identify the boundary type most associated with deep trenches and explosive volcanoes.

Convergent boundary with subduction. One plate sinks beneath another, causing deep quakes and melting.
What is the primary evidence that plates move, based on earthquake locations?

Earthquakes cluster along plate boundaries. Seismic activity maps out plate edges where stress builds.
What is the evidence from GPS measurements that plates are moving today?

GPS shows plates moving a few centimeters per year. Direct measurement confirms plates move at fingernail-growth speeds.
Which boundary type most directly creates deep-ocean trenches by subduction?

Convergent boundary. Denser oceanic plate sinks, forming trenches and volcanic arcs.
What does GPS measurement provide as evidence for plate motion?

Direct measurements of plate movement rates and directions. Satellites track plate positions showing centimeters/year motion.
What is the key fossil evidence that supports past continental connection and plate motion?

Matching fossils on continents now separated by oceans. Same species couldn't cross oceans, proving continents were once connected.
Which option best explains a chain of volcanoes where the youngest volcano is at one end?

Plate moved over a stationary hot spot. Fixed hot spot creates age progression as plate moves over it.
What evidence from earthquake depth patterns indicates subduction at a convergent boundary?

Earthquakes get deeper inland along a dipping zone (Wadati-Benioff). Descending plate creates progressively deeper quakes as it sinks.
What type of boundary forms when two plates move away from each other?

Divergent plate boundary. Plates separate at divergent boundaries, creating new crust.
Which plate boundary type is identified by new crust forming and mostly shallow earthquakes?

Divergent boundary. Plates separate, magma rises to fill gap, creating new oceanic lithosphere.
What boundary type is indicated by a rift valley and basaltic volcanism on land?

Divergent boundary (continental rifting). Continental crust splits, creating valleys and basalt flows.
Identify the boundary: a line of deep earthquakes slopes downward beneath a continent.

Convergent boundary with subduction zone. Earthquakes trace the descending slab as it sinks into the mantle.
What is the evidence from ocean crust age that supports seafloor spreading?

Youngest crust at ridges; older crust farther away. Age increases with distance from ridge, proving seafloor spreading.
What pattern of seafloor rock age supports seafloor spreading?

Youngest at ridges; older farther from ridges. New crust forms continuously at ridges, aging as it moves away.
Identify the plate-boundary type: one plate sinks beneath another, forming a trench.

Convergent boundary (subduction zone). One plate descending beneath another defines oceanic-continental convergence.
What is the evidence from magnetic stripes on the seafloor that supports seafloor spreading?

Symmetric bands of normal and reversed magnetism on both sides. Earth's magnetic field reversals recorded as crust forms.
What does a hotspot island chain (older islands farther from the active volcano) indicate?

Plate moved over a relatively stationary mantle hotspot. Fixed magma source creates age-progressive island trail.
Identify the evidence type: GPS shows two stations on different plates move apart each year.

Direct measurement of plate motion using GPS. GPS precisely tracks current plate velocities in real-time.
What is the main source of heat that drives mantle convection and plate motion?

Earth's internal heat, mainly from radioactive decay and residual heat. Radioactive elements decay and release energy that heats the mantle.
What is the main driving mechanism that transfers heat and helps move plates over time?

Convection currents in the mantle. Hot material rises, cool material sinks, dragging plates along.
What is the evidence from volcano locations that outlines many plate boundaries?

Volcanoes form belts near subduction zones and ridges. Magma rises where plates diverge or one subducts beneath another.
Which evidence most directly measures present-day plate motion rates and directions?

GPS measurements of plate movement. Satellites track plate positions showing 2-10 cm/year movement.
What is a divergent plate boundary?

A boundary where plates move away from each other. Separation creates rifts and mid-ocean ridges.
What rock evidence supports plate motion when mountain belts and rock layers match across oceans?

Matching rock types and mountain ranges. Continuous geological features split by plate movement.
Identify the evidence pattern: earthquakes get deeper inland from an океan trench. What does this show?

A subducting plate descending beneath another plate. Wadati-Benioff zone traces plate's path into mantle at convergent boundaries.
What evidence on continents (besides fossils) supports past connections between landmasses?

Matching rock layers and mountain belts across oceans. Continuous geological features split by ocean basins prove past continental connections.
Which plate boundary type is identified by shallow earthquakes and lateral offset of features?

Transform boundary. Plates slide horizontally past each other without creating or destroying crust.
What is the main driving mechanism that moves tectonic plates over time?

Convection currents in Earth's mantle (asthenosphere). Hot material rises and cool material sinks, creating circular flow that drags plates.
What is subduction?

One plate sinks beneath another into the mantle. Denser oceanic crust descends at convergent boundaries.
Which boundary type is indicated by a chain of volcanoes parallel to a deep-ocean trench?

Convergent boundary with subduction. Subducting plate melts, creating arc volcanoes.
What boundary type is indicated by deep-focus earthquakes that get deeper inland from a trench?

Convergent boundary with subduction. Descending plate generates deeper quakes as it sinks into the mantle.
What evidence from the ocean floor shows new crust forms and plates move apart?

Symmetric magnetic stripes on both sides of mid-ocean ridges. Reversals in Earth's magnetic field create a barcode pattern as new crust forms.
What is the main evidence that plates are moving today, measured directly on Earth's surface?

GPS measurements of plate motion. Satellites track precise plate positions over time.
Identify the boundary: two plates slide past; earthquakes are shallow and frequent.

Transform boundary. Lateral motion causes shallow quakes without volcanism.
What climate evidence supports past continental movement?

Glacial deposits and scratch marks in now-warm regions. Ancient ice evidence in tropics shows continents moved from polar regions.
Which plate boundary type creates new crust and is supported by seafloor spreading evidence?

Divergent boundary. Plates separate, creating space filled by rising magma.
Identify the boundary type: two plates collide and one sinks beneath the other.

Convergent boundary (subduction zone). Oceanic plate descends into mantle, melting creates volcanoes.
Which boundary type is identified by deep ocean trenches and volcanic arcs?

Convergent boundary with subduction. Oceanic plate descends beneath another, creating trenches and melting that forms volcanoes.
Which evidence on the seafloor shows new crust forms at mid-ocean ridges?

Youngest ocean rocks are closest to the ridge. Age increases with distance from ridge, proving new crust forms there.
Which surface feature most directly marks a subduction zone on the ocean floor?

Deep-ocean trench. Deepest parts of ocean formed by subducting plate.
Which boundary type is identified by deep-ocean trenches and subduction?

Convergent boundary. Oceanic plate sinks beneath another, forming deep trenches.
What is the main evidence-based idea called that continents were once joined and later separated?

Continental drift. Wegener's hypothesis based on matching fossils, rocks, and coastlines across oceans.
What climate evidence supports past continental positions near different latitudes?

Glacial deposits/striations in now-warm regions. Ice sheets form only in cold climates, showing continents moved from poles.
Identify the boundary type: Earthquake epicenters form a straight line with little volcanism.

Transform boundary. Horizontal sliding releases energy as earthquakes, not volcanism.
What is a transform plate boundary?

A boundary where plates slide past each other. Lateral motion causes earthquakes but no crust creation or destruction.
Which statement is the best evidence that plates have moved over millions of years: matching fossils, GPS, or tides?

Matching fossils on continents now separated by oceans. Fossils show ancient connections before continents drifted apart.
Which boundary type is most associated with strong earthquakes but little to no volcanism?

Transform boundary. Sliding motion causes earthquakes but no magma generation.
What is the best evidence that continents were once connected, based on continental shape?

Continental coastlines fit together like puzzle pieces. Matching edges suggest continents broke apart and drifted.
Which seafloor feature is the main location where new oceanic crust is created?

Mid-ocean ridge. Underwater mountain chain where plates diverge.
What force helps push plates away from an elevated mid-ocean ridge?

Ridge push. Gravity on elevated ridge causes plates to slide away.
Which seafloor age pattern is evidence that ocean crust moves away from ridges over time?

Youngest crust at ridges; older crust farther from ridges. Dating shows crust age increases with distance from ridge.
What is a hotspot track, and what does it indicate about plate motion?

A volcanic island chain showing plate direction over a mantle plume. Stationary plume creates age-progressive chain as plate moves overhead.
What major landform is typically created at a divergent boundary on a continent?

A rift valley. Continental crust stretches and drops, creating a depression.
What plate-motion process is suggested by earthquakes that get deeper inland from a trench?

Subduction of an oceanic plate beneath another plate. The descending plate creates deeper quakes as it angles down into the mantle.
Which side of a mid-ocean ridge has older basalt: at the ridge or $500\ \text{km}$ away?

The crust $500\ \text{km}$ away is older. Seafloor ages as it spreads away from the ridge where it formed.
What is seafloor spreading?

New oceanic crust forms at mid-ocean ridges and moves outward. Magma rises at ridges, solidifies, and pushes older crust away.
What is the primary heat source that drives mantle convection in Earth?

Heat from Earth's interior, mainly radioactive decay and residual heat. Radioactive elements decay and leftover formation heat create convection currents.
What magnetic pattern in seafloor basalt is key evidence for seafloor spreading?

Symmetric magnetic stripes on both sides of ridges. Mirror-image pattern proves crust forms equally on both sides of spreading center.
Which option best matches boundary type to evidence: ridge, trench, or strike-slip fault?

Ridge = divergent; trench = convergent; strike-slip = transform. Each feature uniquely identifies its boundary type.
What is the name of the plate motion evidence where continents fit together like puzzle pieces?

Continental fit. Coastlines match when continents are reassembled.
What direct modern measurement provides present-day plate motion speed and direction?

GPS measurements of plate movement. Satellites track precise plate positions, showing movement rates of cm/year.
What is a hot spot in plate tectonics?

A long-lived mantle plume that forms volcanoes. Stationary heat source creates volcanic chains as plates move.
Identify the boundary type: two plates move apart and basaltic volcanism occurs at a ridge.

Divergent boundary. Separation creates rift where basaltic magma erupts.
How does a hot-spot island chain provide a direction of plate motion?

Volcano ages increase away from the currently active hot spot. Plate motion carries older volcanoes away from the active hot spot.
What causes the alternating magnetic stripes recorded in basalt on the seafloor?

Earth's magnetic field reversals during crust formation. Basalt records field direction when cooling.
What type of boundary is best supported by evidence of frequent shallow earthquakes along a fault line?

Transform plate boundary. Plates slide past each other horizontally without creating or destroying crust.
What fossil evidence strongly supports that continents were once connected?

Identical fossils found on continents now far apart. Land organisms couldn't cross oceans, proving continents were joined.
What is the best evidence that continents were once connected, based on fossil distribution?

Matching fossils found on widely separated continents. Same species couldn't cross oceans, proving continents were joined.
What is subduction, and what evidence shows it is happening?

One plate sinks; deep-ocean trenches and deep earthquakes form. Denser oceanic plate descends beneath another plate.
Identify the boundary type: a deep ocean trench plus a volcanic arc on the overriding plate.

Convergent boundary with subduction. Oceanic plate sinks beneath another, creating trenches and arc volcanoes.
What driving force pulls a dense oceanic plate into the mantle at a subduction zone?

Slab pull. Gravity acts on cold, dense subducting lithosphere, pulling the plate down.
What evidence from matching rock layers and mountain belts supports past plate movement?

Same rock types and structures on now-separated continents. Continuous features split when ancient landmasses broke apart.
What evidence shows that continents were once connected (continental drift)?

Matching fossils and rock layers on widely separated continents. Same species couldn't cross oceans; continents must have been joined.
Which plate boundary type destroys crust and is supported by trench evidence?

Convergent boundary with subduction. Oceanic crust recycled back into mantle at trenches.
What evidence indicates two continental plates have collided rather than subducted?

Large folded mountain ranges with little volcanic activity. Continental crust is too buoyant to subduct, so it crumples upward.
What is seafloor spreading?

Creation of new oceanic crust at mid-ocean ridges. Magma rises at ridges, solidifies, pushes plates apart.
What causes the magnetic stripes recorded in basalt at mid-ocean ridges?

Geomagnetic reversals recorded as lava cools and solidifies. Iron minerals align with Earth's magnetic field when magma cools.
What evidence from matching continents supports that plates have moved over geologic time?

Continental "jigsaw-fit" (for example, South America and Africa). Coastlines fit together like puzzle pieces when continents are reassembled.
Identify the boundary type where one plate sinks beneath another.

Convergent boundary with subduction. Denser oceanic plate descends beneath less dense plate.

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