Science: Plate Tectonics and Earthquakes
How moving plates shape Earth's surface
Science: Plate Tectonics and Earthquakes
How moving plates shape Earth's surface
Science - Grade 6-8
- 1
What is a tectonic plate?
Think about the outer rocky shell of Earth being broken into pieces.
A tectonic plate is a large, rigid section of Earth's lithosphere that moves slowly over the softer layer beneath it. - 2
Name the three main types of plate boundaries.
The three main types of plate boundaries are divergent boundaries, convergent boundaries, and transform boundaries. - 3
Describe what happens at a divergent plate boundary.
This type of boundary pulls apart.
At a divergent plate boundary, two tectonic plates move away from each other, often allowing magma to rise and form new crust. - 4
Describe what happens at a convergent plate boundary.
At a convergent plate boundary, two tectonic plates move toward each other, which can cause subduction, mountain building, or volcanic activity. - 5
Describe what happens at a transform plate boundary.
The plates grind sideways.
At a transform plate boundary, two tectonic plates slide past each other, which can create stress that is released as earthquakes. - 6
What causes most earthquakes?
Most earthquakes are caused by the sudden release of energy when built-up stress along faults or plate boundaries causes rocks to break or slip. - 7
What is a fault?
It is often the place where earthquake movement happens.
A fault is a crack in Earth's crust where rocks move past each other. - 8
Explain the difference between the focus and the epicenter of an earthquake.
The focus is the point inside Earth where the earthquake begins, and the epicenter is the point on Earth's surface directly above the focus. - 9
How can the movement of tectonic plates build mountains?
Think about what happens when crust is squeezed.
Tectonic plates can build mountains when plates collide and push Earth's crust upward, folding or uplifting the land. - 10
Why are many earthquakes found near plate boundaries?
Many earthquakes are found near plate boundaries because that is where plates interact, build up stress, and suddenly release energy. - 11
A student says that continents float on melted rock like boats on water. Is this fully correct? Explain.
The layer below the plates is solid rock that can flow slowly over time.
This is not fully correct because tectonic plates move over the softer, slowly flowing asthenosphere, but they do not float on completely melted rock like boats on water. - 12
What evidence supports the idea that Earth's plates move over time?
Evidence that Earth's plates move includes matching fossils on different continents, the fit of continental coastlines, patterns of earthquakes and volcanoes, and seafloor spreading. - 13
How does seafloor spreading provide evidence for plate tectonics?
New ocean crust forms at ridges and moves away from them.
Seafloor spreading provides evidence for plate tectonics because new crust forms at mid-ocean ridges and moves outward, showing that plates are separating and carrying the seafloor with them. - 14
A map shows frequent earthquakes along the west coast of South America. What does this suggest about the plate boundary there?
This suggests that the west coast of South America is near an active plate boundary, likely a convergent boundary where one plate is being forced beneath another. - 15
Explain one way people can reduce earthquake damage in cities.
Think about engineering and safer buildings.
People can reduce earthquake damage in cities by designing and building structures that can better absorb shaking, which helps prevent collapse during an earthquake.