Post on 16-Feb-2016
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The Earth’s Interior
• Crust (Lithosphere)• Mantle• Outer Core• Inner Core
Inner Core• The deepest part of the
earth (1512 miles deep) is a solid that contains both iron and nickel.
• It is because of this that the center of the earth is a magnet, a compass.
• It generates a magnetic field that protects the earth from flying out of orbit.
Outer Core• Outside of the inner core
lays the outer core (1419 miles deep).
• This is much like the inner core with the exception that it is a liquid that contains sulphur and oxygen (which lowers the melting point).
Mantle• Occupying 1789 miles of
the earth is the magma (iron and magnesium) that makes up the mantle.
• Upper and lower• It is extremely hot!!• goopy; very plastic-like.
(upper mantle)• Mostly solid (lower
mantle)
Crust• Also called lithosphere• This is the top layer of the
earth, which is basically hardened mantle (magma).
• It contains two segments, the oceanic and continental crusts.
• Note: this is the same crust, it just depends how thick it is to determine if it is part of the Oceanic or Continental Crust.
Read About Earth’s interior
• Our Text p. 4-6
Theory Of Continental Drift• Alfred Wegener
• It is this German man to whom we credit with the proposal of the theory of Continental Drift.
• While pondering the similarities between the coastlines of South America and Africa, Wegener came up with an idea:
• What if the continents were once all connected and just drifted over the years?
Wegener’s Proof
Wegener’s Proof
Wegener’s Proof
The Flaw in Wegner’s Theory
• He thought that each of the continents were a separate plate--they were just drifting on a never-changing ocean.
• Like styro-foam floating on a pool of water!!
Missing Proof
• Wegener could not explain what mechanism was powerful enough to move huge continents
• Scientist’s never believed him
Canadian Correction• J. Tuzo Wilson
• the 1960’s Canadian scientist who resurrected Wegner’s theory after years of disbelief by the science community.
• Today, we know that that's false, thanks to the discovery of crustal plates.
• The plates of the earth are not composed of just land; they're composed of ocean too.
Canadian Correction – cont’d
• In some cases, the plates are just land, in others they're just ocean, and, in still other cases, they consist of land and ocean.
• They each have different boundaries and move in all different directions.
Plates of the earth p. 12
Continental Drift
• refers to the movement of the more than 20 plates (9 major) due to convergent, divergent, and transform boundaries.
• The continents drift at a rate of 2 inches a year.
• Started 200 million years ago
• Pangea (land) & Panthalasa (sea)
Plate Tectonics
• Tectonic plates move or float on top of the upper mantle.
• However they do not float freely.
• The plates are forced in specific directions by the flow of magma beneath.
Plate Tectonics – cont’d• Plates move with the flow of magma.
• The magma closer to the core heats and then rises towards the surface as its density decreases.
• Once the rising magma reaches the lithosphere it moves in opposite directions.
• The magma forms convectional currents.
Convection Currents
Plate Tectonics – Convection Currents
Divergent Boundaries
• Tensional Forces occur where two tectonic plates are pushed apart. The tension is created as the plates move away from each other.
• Ridge Zones sometimes occur where two plates move apart. The magma rises between the plates and forms a ridge.
• Again caused by convectional currents in the magma
Tensional Forces – Ridge Zones
This diagram above shows “Sea Floor Spreading”
Where’s the TENSION?
Convergent Boundaries
• Compressional Forces occur where two tectonic plates come together. They compress against each other.
• Subduction Zones sometimes occur where compressional forces result from two plates colliding and one plate slips under the other.
• Again caused by convectional currents in the magma
Compressional Forces – Subduction
Where’s the Subduction / Compression?