Plate Boundaries Overview

Overview

This lesson covers the three main types of plate boundaries—divergent, convergent, and transform—describing their processes, results, and examples.

Plate boundaries are the lines at the edges of lithospheric plates where intense geologic activity occurs.
Plates move due to convection currents in Earth's mantle, causing interactions at boundaries that lead to earthquakes, volcanoes, and mountain building.

Divergent boundaries form when two tectonic plates move away from each other, creating tension and new crust.
Magma rises to fill the gap, solidifying into new oceanic crust, forming mid-ocean ridges and rift valleys.
Example: The Mid-Atlantic Ridge between the Eurasian and North American Plates.

Convergent boundaries occur when two plates move toward each other, causing subduction or compression.
Oceanic-Continental: Oceanic plate subducts beneath continental plate, forming trenches and volcanic activity.
Oceanic-Oceanic: One oceanic plate subducts under another, forming deep oceanic trenches and volcanic island arcs.
Continental-Continental: Both plates crumple, resulting in mountain ranges like the Himalayas.

Transform boundaries form when two plates slide horizontally past each other, causing earthquakes.
These are also called strike-slip faults.
Example: San Andreas Fault between the Pacific and North American Plates.

Divergent: Plates move apart; example—Mid-Atlantic Ridge.
Convergent: Plates move together; examples—Himalayas (continental-continental), oceanic trench (oceanic-oceanic).
Transform: Plates slide past each other; example—San Andreas Fault.

Plate Boundary — The edge where two tectonic plates meet.
Divergent Boundary — Plates move apart, creating new crust.
Convergent Boundary — Plates move towards each other, causing subduction or compression.
Subduction — Process where one plate moves beneath another into the mantle.
Transform Boundary — Plates slide past each other horizontally.
Mid-Ocean Ridge — An underwater mountain system formed by divergent boundaries.
Trench — Deep depression in the ocean floor formed at subduction zones.
Compression — The process of plates pressing together, thickening the crust.

Review the lesson and complete any related exercises or tables provided during the activity.
Prepare for the next lesson by recalling real-world examples of each plate boundary type.