Plate Boundaries
Explain how plate boundaries cause earthquakes and volcanoes: plates pushing together, pulling apart, or sliding past each other create the forces that trigger these events, and mountains form where plates collide
What a learner can do afterwards
- Describe three types of plate boundary movement: convergent, divergent, and transform
- Explain that earthquakes occur when plates grind or collide at boundaries
- Explain that volcanoes form where plates pull apart or one slides under another, allowing magma to rise
The lesson
You already know Earth is covered in huge plates that drift on hot rock. The place where two plates meet is called a boundary. Plates can push together, pull apart, or slide past each other. Each kind of boundary causes different things: earthquakes, volcanoes, or new mountains.
At a convergent boundary, plates push together. Often, one plate gets pushed underneath the other and sinks into the hot rock below. It melts into magma, which rises up and can erupt as a volcano. Sometimes two thick pieces of land crash into each other instead. Neither one sinks, so the land squeezes upward into tall mountains.
At a divergent boundary, plates pull apart and leave a gap. Magma rises up to fill that gap and cools into new crust, often deep under the ocean. At a transform boundary, plates slide past each other sideways. The rock usually sticks instead of gliding smoothly, and when it finally slips, the ground jolts in a sudden earthquake.
Along the San Andreas Fault in California, two plates grind past each other at a transform boundary. The rock stays stuck for years while pressure builds. When it finally slips, the ground shakes in an earthquake, even though there is no volcano nearby.
To remember the three kinds: push together can raise mountains or feed volcanoes, pull apart grows new crust and volcanoes, and slide past mostly causes earthquakes.
Plates push together, pull apart, or slide past each other, and each kind of edge makes its own earthquakes, volcanoes, or mountains.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.