Tectonics Flashcards
What is Geomorphology? What does it study specifically?
It is the science of landforms. It studies the origin, evolution, form, and spatial distribution
How are landscapes formed?
Through the interactions between endogenic and exogenic processes
Are plate tectonics an endogenic or exogenic process?
Endogenic
What is the theory of “continental drift” and “pangaea”?
It was a theory by alfred wegener in 1912 and stated that continents floated on plastic material
He though this because:
•Noticed “fit” of the coastlines of the continents
•Found fossils indicating very different climates than today
•Matched large-scale features; e.g., Appalachian rocks match rocks in Scottish Highlands
How was the theory of continental drift and pangaea received?
Hypothesis was harshly rejected by scientific world—no mechanism!
What would drive the movement?
How is the Earth’s surface divided? What drives these movements?
The Earth’s surface is divided into a set of lithospheric plates that are in slow but steady motion. Movement of these plates is driven by heat from the Earth’s core
What are endogenic processes?
Internal processes - work from within the Earth
What are exogenic processes?
External processes - work at the Earth’s surface. I.e, weathering by wind and water
What is the crust? Where is it separated from the mantle?
the thin, outermost layer of the planet. The Earth’s crust is separated from the mantle by the boundary called the Moho.
What happens at the Moho?
Seismic waves indicate that a sudden change in the density of materials occurs. This is due to a change in chemical composition
What is the lithosphere? Where is it thickest and where is it thinnest?
It is the outer earth shell of rigid, brittle rock, including the crust and also the cooler, upper part of the mantle. It ranges in thickness from 60 to 150km, and is thickest under the continents and thinnest under the ocean basins
How does the lithosphere compare to the asthenosphere?
The lithosphere is on top of the asthenosphere, and is a hard, brittle shell resting on a soft, plastic underlayer. The lithosphere floats on the plastic asthenosphere much like an iceberg floats on water.
Who came up for the mechanism of continental drift theory, and what effect did it have on geosciences?
Harry Hess from Princeton. It is a paradigm shift in geosciences
What does seafloor spreading do?
It produces new crust under the sea
What are igneous rocks?
Are formed when molten material or magma solidifies
What are sedimentary rocks?
Sedimentary rocks are made from layers of mineral particles found in other rocks that have been released by weathering. They also include rocks made from newly formed biomass and invertebrates.
What are some common sedimentary rocks?
sandstone, siltstone, conglomerate, mudstone, claystone, shale, limestone, dolomite, chert, evaporites, coal, petrolem, natural gas
What are some common igneous rocks?
rhyolite, granite,diorite, andesite, basalt, gabbro
What are metamorphic rocks?
formed by tremendous high pressures and temperatures that alter igneous and sedimentary rock into metamorphic rock
what are some common metamorphic rocks?
slate, schist, marble, gneiss, quartzite
What is some evidence for Pangaea?
Mirror images of rock ages on each side of a spreading ridge and magnetic reversals in polarity
What is the energy source for Plate Tectonics?
- Earth’s internal heat from the decay of radioactive material
- Convection in the mantle (pushing and pulling)
Presently, how many plates are moving around?
14
What direction do the major plates (N. American, S. American, African, Eurasian, Indo-Australian, Pacific, Antarctic) move?
Look at map on slide 14
What are the 3 boundary types that are between plates and what do they do?
Divergent, convergent, and transform boundaries. They have a strong influence on surface landforms
What is a divergent boundary? Give an example.
New crust is formed as plates move apart and magma rises to surface. “zones of “extension”
new crust is formed as plates move apart”
Surface expression: ridges
Where are most divergent plate boundaries found?
In the middle of oceans
What are convergent boundaries?
zones of “compression”
Plates collide and crust is “recycled”
Where does the old crust go when plates converge?
Subduction. This is the descent of the edge of a lithospheric plate under an adjoining plate and into the asthenosphere
What is subduction?
When an oceanic plate collides with a continental plate, the oceanic plate is subducted into the asthenosphere. This is because the oceanic plate is Oceanic crust is thinner but denser and heavier than continental crust. It always sinks below the thicker, but lighter, continental crust.
Where are subduction zones often found?
Mostly along continental margins
What do these subduction zones mark?
Convergent boundaries that are strongly associated with earthquakes and volcanism
What happens when continental lithosphere meets continental lithosphere?
Orogeny. This is the folding of crust were two continental plates meet contributes to a mountain-building process
In orogeny, how is the crust uplifted?
through folding and faulting
What is a transform plate boundary?
Zones of lateral movement. Plates slide past each other without colliding. NO crust formed or destroyed (just bending, ripping, and faulting)
What are transform boundaries sometimes referred to as?
“Transform faults”
What do many transform faults connect?
segments of spreading ridges
Where do some transform faults occur?
Continental margins
