Test 1: Plate Tectonics Flashcards
Why should we know about plate tectonics?
Plate tectonics affects us all whether it’s by volcanic eruptions and earthquakes or politically and economically due to the distribution of natural resources.
Plate tectonics is the unifying glory of geology, typing together many seemingly unrelated geologic phenomena and illustrating why the earth is a dynamic planet of interacting subsystems and cycles.
What is the Protoearth?
Larger than earth today
Homogenous composition (looked the same the top to the centre)
Bombarded by meteorites
Moon formed from a collision with large astroid.
What happened with the Protoearth?
- Radioactive heat (decay)
- Fusion reactions
- Earth heated up so much that it became molten**
- Lighter elements like hydrogen and oxygen came up to the surface. Heavier elements like nickel and iron migrated to the centre of the core.
Density Satisfaction?
“Divisions of the Earth-based upon physical state are the Lithosphere, Asthenosphere, Mesosphere, Outer core, and Inner core”
How to get layered earth?
The earth being liquid from the top to the core is the only way you can get a layered earth
What are the two categories of layers?
Physical and Chemical properties
What are Chemical Properties made up of?
Chemical Properties:
Crust, Mantle, and core
What are Physical Properties made up of?
Physical Properties:
Lithosphere, Asethonosphere, Mesosphere, Outer Core, Inner Core
What elements make up the core?
Core: Irons and Nicles
What elements make up the crust?
Crust: Oxygen, Silica
What elements make up the mantle?
Mantle: Magnesium
Lithosphere:
Ridgid (Breakable)
Asthenosphere:
Plastic (Applied force will move it)
Mesosphere:
Ridgid
Outer Core:
Liquid
Inner Core:
Ridgid
Describe The Crust:
The outermost layer, the crust; low density, mainly silicate materials
Continental Crust:
Granite (Light coloured igneous rocks) Less Dense
Oceanic Crust:
Basalt (Darker in colour igneous rocks) More Dense
What’s the difference between Granite Rocks and Basalt rocks?
Granite Rocks have crystals in them and are prettier.
Basalt rocks are darker and are not as pretty came to the surface
Describe The Mantle:
The Mantle surrounds the core and is divided into:
- An asthenosphere that behaves plastically and flows slowly.
- Iron, magnesium, silicate materials.
Describe the Core:
The Core consists of a small, solid inner region. A larger, liquid, outer portion.
Flows generate Earth’s magnetic field.
High density, mainly iron and nickel.
Who is Alfred Wegener?
Alfred Wegener first proposed in 1912 - “Continental Drift”
What is “Continental Drift”?
Pangaea consists of a northern landmass called Laurasia and a southern landmass called Gondwana.
Essentially Pangaea was made up of the continents and they broke apart.
What was Wegener’s evidence for continental drift? FC MGL GACB DF
The fit of Continents (Earth is a puzzle)
Matching geological locations (Rocks from one continent, match up with others (mountains )
Glacial ages and climate belts (Movement of glaciers marks up the rocks on the bottom)
Distribution of Fossils (fossils only found in one spot)
What is Pangaea?
One large continent existed 200 million years ago
What is Panthalassa?
One large ocean
The evidence behind continental drift, Matching geological locations?
The similarity in rock sequences
The evidence behind continental drift, Glacial Ages?
Ridges on the bedrock beneath
The evidence behind continental drift, distribution of fossils?
Fossils found on both continents of extinct creatures
Objections to Continental Drift?
Continents can’t plow through ocean basins, Tidal gravitations are too small, proposed mechanisms defy laws of physics.
Paleomagnetism:
Remnant magnetism in ancient rocks recording the direction and intensity of the earth’s magnetic field at the time.
What’s recorded in igneous rocks?
Magnetic Polarity (Magnetite in basalt)
When was the last time earth’s magnetic field was completely reversed?
780,000 years ago
How does Earth’s magnitude reverse over time?
Magma up from underneath the surface and turns into lava, which then comes out of the volcano. The magnetic materials flow out of the volcano and are flipped.
Who is Harry Hess?
Harry Hess was a WW2 submarine captain and geologist
How old is the oldest ocean floor?
180 million years old.
What did Harry Hess propose?
Harry Hess proposed the seafloor spreading. Mantle Convection cells as the mechanism.
Why does the seafloor spread?
Mid-ocean ridge moves apart, magma is pushed up through the layers and turned into lava where then the magnetic materials like magnetite will orientate themselves to where the magnetic pull is.
Both parallel and symmetric around the ocean ridges?
Magnetic anomalies
What is the source of energy for the high temperatures found deep within the Earth?
Radioactive decay- when unstable, atomic nuclei decay, radiant energy is given off.
Plate Tectonics Unifying Theory: Divergent
Divergent: Plates move away from each other (Mid Ocean Ridge) (Shallow at the surface)
Plate Tectonics Unifying Theory: Convergent
Convergent: Where plates approach each other (Deep below the surface)
Plate Tectonics Unifying Theory: Transform
Transform: Where plates slide past each other (San Andreas Faults) (Medium level)
Divergent: Characteristic features of ancient continental rifting include…
faulting, dikes, sills, lava flow, and thick sedimentary sequences within rift valleys.
Evidence of Ancient spreading ridges:
Pillow Lavas and associated deep-sea sediments are evidence of ancient spreadings.
What are the three types of plate Boundarys?
Oceanic-Continental convergence
Oceanic-Oceanic convergence
Continental-Continental convergence
Oceanic-Continental convergence
Ocean plate subducted
Continental arcs generated
Explosive Volcanic Eruptions
Oceanic-Oceanic convergence
The denser plate is subducted
Deep trenches generated
Volcanic island arcs generated
Continental-Continental convergence
No subduction
Tall mountains uplifted
The Himalayas from India-Asia collision
The world’s plants and animals occupy biotic provinces controlled mostly by:
Climate
Geographic barriers
True or False, the older the plate the denser?
True
What is Andesite?
Andesite: an extrusive rock composed between granite and basalt.
What detects plate movements?
Satellites have detected and measured plate movements over time.
Paleogeography:
The study of historical changes of continental shapes and positions
Mineral Depots:
A mineral deposit is simply an enriched body of rock with a particular metal or mineral of economic (or strategic) interest that could be considered for mining.
The most common metallic ore depots to find are…
Copper, Iron, lead, zinc, gold and silver ore
Oceanic Transform Faults
Ocean floor only
Continental Transform faults
Cuts across the continent (San Andreas Fault)
Transform Faults occur between mid-ocean ridge segments
