Key concepts. Earth Composition. Crust: thinnest layer, least dense Mantle: upper most part is able to flow very slowly (asthenosphere) Core: Lower area is a solid and outer area is a liquid. Makes up 1/3 of Earth’s mass. The hottest layer with the most pressure.
Crust: thinnest layer, least denseMantle: upper most part is able to flow very slowly (asthenosphere)
Core: Lower area is a solid and outer area
is a liquid. Makes up 1/3 of Earth’s mass.
The hottest layer with the most pressure.
What evidence supports the theory of continental drift?
Shoreline Fit of the Continents
The fossils from the exact same animals are found on continents separated by vast oceans.
Glaciers scars are found on continents which are today too warm for glaciers.
Why are the continents moving?
The oceans are widening along the mid-ocean ridges.
Plates—continental crust, oceanic crust
Features—faults, trenches, mid-ocean ridges, folded mountains, hot spots, volcanoes
Related actions —earthquakes, volcanic activity, seafloor spreading, mountain building, convection in mantle.
Two land or ocean plates move apart in opposite directions. Magma flows to the surface between them creating new crust.
Subduction zones form chains of volcanic mountains along the shoreline.
Two continents hit head-on, crinkling up the land into a high mountain chain.
The Himalayas Are Born…
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.
Forces—tension, compression shearing
Ask a Geologist
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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).