1 Only three
- <b>Apart</b> → divergent.
- <b>Toward</b> → convergent.
- <b>Past</b> → transform.
- Every boundary on Earth is one of these three.
"Which way are they moving?"
2 Apart — divergent
- A ridge under the sea; a rift valley on land.
- <b>New crust is made here, and only here.</b>
- Shallow earthquakes.
- Frequent, gentle eruptions — runny lava.
"Youngest rock in the middle."
3 Toward — and it depends
- <b>Ocean + continent:</b> trench, volcanic mountains.
- <b>Ocean + ocean:</b> trench, island arc.
- <b>Continent + continent:</b> huge mountains, <b>no trench, no volcanoes</b>.
- Deep earthquakes wherever a plate sinks.
"What crust is arriving?"
4 Past — and the two traps
- <b>Transform:</b> a fault, offset streams and roads. Nothing built — and shallow, destructive quakes.
- ❌ The plates do <b>not</b> float on liquid magma. The asthenosphere is solid rock that flows.
- ❌ <b>Not</b> every convergent boundary has a trench.
"Nothing built is not nothing happening."