15 Questions
What is plate tectonics?
The theory that the surface of the earth is broken into larger pieces of crust called plates that ride along on a softer layer of the earth
What is the thickness of continental plates?
Up to 150 km
What is the thickness of oceanic plates?
5-10 km
What is the softer layer of the earth that the plates ride along on?
Asthenosphere
Who proposed the theory of plate tectonics?
Geologists
What do geologists study?
The earth
What is the upper part of the mantle called?
Asthenosphere
What is the main cause of plate movement according to the text?
Radioactive decay of uranium and other elements in the core
What is the mantle's composition mainly made of?
Oxygen, silicon, magnesium, and iron
What is the crust or lithosphere likened to in the text?
The peel of an apple
What causes the plates to move according to the text?
Convection currents in the mantle
What happens when convection currents encounter the thin crust at the top of the mantle?
It causes the crust to move
What is ridge push, as described in the text?
Plates higher at the spreading center flow downhill due to gravity
What causes oceanic crust to be forced under another plate according to the text?
Gravity pulling the denser oceanic crust downward
How are deep ocean trenches formed according to the text?
By one tectonic plate sliding under another
Study Notes
Plate Tectonics
- Plate tectonics is the theory that the Earth's surface is divided into large plates that move relative to each other, resulting in geological phenomena such as earthquakes, volcanoes, and mountain ranges.
Plate Thickness
- Continental plates are approximately 100-200 km thick.
- Oceanic plates are approximately 50-100 km thick.
Earth's Layers
- The softer layer of the Earth that the plates ride along on is the asthenosphere.
- The upper part of the mantle is called the lithosphere.
The Theory of Plate Tectonics
- The theory of plate tectonics was proposed by Harry Hess.
Geologists' Focus
- Geologists study the Earth's surface and the processes that shape it.
Plate Movement
- The main cause of plate movement is convection currents in the mantle.
- The mantle's composition is mainly made of hot, viscous rock.
- The crust or lithosphere is likened to a thin, brittle layer of ice on top of a soft, warm lake.
Plate Movement Causes
- Convection currents in the mantle cause the plates to move.
- When convection currents encounter the thin crust at the top of the mantle, they push the plates.
Ridge Push
- Ridge push is the process by which new crust is formed at mid-ocean ridges, causing the plates to move away from the ridge.
Oceanic Crust Subduction
- Oceanic crust is forced under another plate at deep-sea trenches due to the density difference between the two plates.
Deep Ocean Trenches
- Deep ocean trenches are formed when oceanic crust is forced under another plate at a subduction zone.
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