Changing Earth Surface - Middle School Earth and Space Science
- Identify the relative age: Is a fault younger or older than the rock layers it cuts through?
- Younger. The fault formed after the layers it disrupts.
- What surface evidence most directly supports that an unconformity formed between two rock layers?
- An irregular erosional boundary separating older and younger layers. Erosion creates uneven surfaces between rock units.
- What is a fossil, and why is it useful evidence for past surface environments?
- Preserved remains/traces; indicates past conditions and depositional setting. Shows what lived there and environmental conditions.
- Which evidence best supports that a region was once desert-like: dune cross-beds, coral fossils, or pillow basalts?
- Dune cross-beds. Wind-blown sand forms angled layers in desert dunes.
- What is the best evidence that frost wedging (ice) is breaking rock apart?
- Cracks widened with angular fragments at the base of slopes. Water freezes in cracks, expands, and breaks rock mechanically.
- What does a sedimentary rock layer (stratum) most directly indicate about past conditions?
- Sediments were deposited over time, often in water or wind environments. Layers form from particles settling in specific environments.
- Which landform is strongest evidence of wind deposition: delta, dune, or moraine?
- Dune. Wind deposits sand in characteristic mound shapes.
- Which principle states that in undisturbed sedimentary layers, the oldest layer is at the bottom?
- Law of Superposition. Sediments settle in order, creating a time sequence.
- Which evidence best supports coastal erosion over time when comparing photos years apart?
- Shoreline retreat and loss of beach or cliff material. Waves remove material, causing land to move inland.
- Which relative-age rule states: a fault or igneous intrusion is younger than the rocks it cuts?
- Principle of cross-cutting relationships. Features must exist before being cut through.
- What is the best evidence that chemical weathering is occurring on a statue or headstone?
- Pitting and surface dissolution on limestone or marble. Acid rain reacts with carbonate minerals, creating holes.
- Which relative-age rule states: in undisturbed layers, older rocks are below younger rocks?
- Law of superposition. Sediments deposit sequentially, oldest at bottom.
- Which agent of erosion is most likely if you observe V-shaped valleys and meandering streams?
- Running water. Rivers cut V-shaped valleys and create winding channels.
- If Layer A lies above Layer B in undisturbed rock, which layer is older?
- Layer B. Lower layers formed first in undisturbed sequences.
- Which agent of erosion is most directly supported by V-shaped valleys and meandering streams?
- Running water (rivers/streams). Flowing water cuts narrow valleys and creates curved channels.
- What is a fossil, and why is it evidence of surface change over time?
- Preserved remains/trace; shows past environments different from today. Past life forms preserved in rock reveal environmental changes.
- Which plate boundary most often creates mountain ranges through compression and uplift?
- Convergent plate boundary. Colliding plates compress and fold crust upward.
- Which process is indicated when a river slows and drops sediment at its mouth?
- Deposition. Reduced velocity causes rivers to drop their sediment load.
- What landform provides evidence of long-term deposition where a river enters an ocean or lake?
- Delta. Triangular sediment buildup shows continuous deposition.
- What is the main long-term effect of plate tectonics on Earth's surface?
- It builds and reshapes crust through mountain building, earthquakes, and volcanism. Plate movements create mountains and trigger volcanic/seismic activity.
- Identify the relative age: In undisturbed layers, is Layer A older if it is below Layer B?
- Yes, Layer A is older than Layer B. Superposition places older layers beneath younger ones.
- What is mass wasting?
- Downhill movement of rock and soil due to gravity. Gravity alone moves material downslope without other agents.
- Which process forms rounded pebbles in a river: weathering, erosion, or deposition?
- Weathering (abrasion). Water tumbling rocks against each other smooths their surfaces.
- Which term means rock is broken down but not moved: weathering, erosion, or deposition?
- Weathering. Breaking occurs in place without transportation.
- Which agent of erosion is most likely if you observe U-shaped valleys and moraines?
- Glaciers (ice). Glaciers carve distinctive U-shaped valleys and leave debris piles.
- What is an unconformity?
- A gap in the rock record caused by erosion or nondeposition. Missing time represents erosion or no sediment deposited.
- Which agent of erosion is most directly supported by U-shaped valleys and moraines?
- Glaciers (ice). Ice carves wide, rounded valleys and deposits unsorted debris.
- Which agent of erosion is most likely if you observe talus piles at the base of a steep slope?
- Gravity (mass wasting). Gravity pulls loose rock downslope, forming debris piles.
- Which evidence best supports that a region was once underwater: ripple marks, lava flows, or dune cross-beds?
- Ripple marks. Wave action creates ripples in underwater sediments.
- What is uplift, and how does it change Earth's surface over time?
- Rising of crust; increases elevation and can increase erosion rates. Tectonic forces raise land, exposing it to weathering.
- Which agent of erosion is most likely if you observe sand dunes and wind-shaped rocks?
- Wind. Wind sorts sand into dunes and abrades exposed rocks.