Earth Systems & Layers
Why can tectonic plates move even though rock is solid?
Answer: Plates move because the mantle beneath them slowly flows.
Question: Why do South America and Africa support continental drift?
Answer: Their coastlines fit together like puzzle pieces.
Question: What major feature forms where plates move apart?
Answer: Mid-ocean ridges or rift valleys.
Question: What happens when plates collide?
Answer: They push together and one may subduct.
Question: How do plates move at transform boundaries?
Answer: They slide past each other.
Question: Which Earth layer allows plates to slowly move above it?
Answer: The asthenosphere.
Question: Identical fossils found on different continents suggest what?
Answer: The continents were once connected.
Question: Why does magma rise at divergent boundaries?
Answer: Pressure decreases, allowing magma to rise.
Question: Why does oceanic crust usually subduct under continental crust?
Answer: Oceanic crust is denser.
Question: Why is crust not created or destroyed at transform boundaries?
Answer: Plates move sideways instead of colliding or separating.
Question: Explain why the lithosphere breaks instead of bending easily.
Answer: The lithosphere is rigid and brittle, so it cracks under stress.
Question: Why are rocks youngest near mid-ocean ridges?
Question: Why are rocks youngest near mid-ocean ridges?
Question: What happens to an ocean basin over millions of years at a divergent boundary?
Answer: The ocean becomes wider.
Question: What forms when two continental plates collide?
Answer: Mountain ranges.
Question: Why do earthquakes commonly occur at transform boundaries?
Answer: Friction builds stress that releases suddenly.
Question: If mantle movement stopped, what would happen to plate motion?
Answer: Plate movement would stop and earthquakes, volcanoes, and mountain building would decrease.
Question: Magnetic stripes on both sides of ridges prove what?
Answer: Sea-floor spreading is occurring.
Question: A scientist finds young rock and thin sediment. Where are they likely located?
Answer: Near a mid-ocean ridge.
Two plates collide. One is oceanic and one is continental. Describe what happens to EACH plate and explain what landforms are created.
The denser oceanic plate subducts beneath the continental plate.
A trench forms at the boundary, and volcanoes form on the continent because melting occurs in the mantle
Question: What would happen if friction disappeared along a transform fault?
Answer: Fewer or weaker earthquakes would occur.
Question: Predict how Earth would look if density separation never happened early in Earth’s history.
Answer: Earth would not have layers and plate tectonics might not occur.
Question: Why did scientists need multiple types of evidence before accepting plate tectonics?
Answer: One piece of evidence was not enough; fossils, rock ages, and magnetic data together proved plate movement.
Question: Explain how divergent boundaries create new crust.
Answer: Plates separate, magma rises, cools, and forms new oceanic crust.
Question: An area has trenches, earthquakes, and volcano chains. What boundary is this?
Answer: Convergent boundary because subduction occurs.
Question: Compare convergent, divergent, and transform boundaries.
Convergent → collide, crust destroyed
Divergent → move apart, crust created
Transform → slide past, crust unchanged