Iceland – a continent directly over the Mid-Atlantic Ridge
Subduction Zones An ocean plate and a continental plate hit head-on. The ocean plate subducts under the continent forming a trench. The subducting plate melts. Magma rises to the surface creating a string of volcanic mountains parallel to the shoreline.
Andes Mountains Subduction zones form chains of volcanic mountains along the shoreline.
Collision Zones Two continents hit head-on, crinkling up the land into a high mountain chain.
India’s Collision with Asia Himalayas
The Himalayas Are Born…
Island Arcs Two ocean plates hit head-on. One ocean plate is forced to subduct under the other forming an ocean trench. The subducting plate melts. Magma rises to the surface forming a string of volcanic islands parallel to the trench.
The Aleutian Islands
Forces —tension, compression shearing Key concepts Ask a Geologist Ask an earth scientist
How does tectonic activity affect the earth’s crust? Builds mountains Creates deep ocean trenches Causes earthquakes Create volcanoes
Recent patterns of earthquake and volcanic activities; maps showing the direction of movement of major plates and associated earthquake and volcanic activity Compressional boundaries: folded mountains, thrust faults, trenches, lines of volcanoes (e.g. Pacific “ring of fire”) Tensional boundaries: mid-ocean ridges, rift valleys Shearing boundaries: lateral movement producing faults (e.g. San Andreas Fault). Real-world contexts: