Plate Tectonic Theory
The solid, rigid layer of Earth's crust that makes up the "plates" of plate tectonics
Lithosphere
The 3 types of plate boundaries.
Divergent, Convergent and Transform
The process that causes tectonic plates to move?
Convection Currents.
Plate Boundaries
Define Speed/Velocity
The distance something travels over time
The weak-solid/plastic layer of Earth on which the plates move.
Asthenosphere
A plate boundary where two tectonic plates spread apart and move away from each other.
Divergent Boundary
Molten material in the mantle rises and falls due to changes in ________
Density
A divergent boundary forms what type of features (2 examples)
Mid-ocean ridge, earthquakes, volcanoes, rift valleys, oceans
What is the equation for Speed?
Speed = Distance divided by Time
S = D / T
The outermost layer of the Earth that includes all of the features on Earth's surface and is made up of the crust and the uppermost part of the mantle.
Lithosphere
A plate boundary where two plates collide and move towards one another and a geologic feature that forms as a result.
Convergent Boundary. Forms mountain ranges, volcanoes, earthquakes, deep-ocean trenches, island arcs, subduction zones.
What causes molten material in the mantle sink back down towards Earth's core at subduction zones? 3 parts
1. It becomes cooler
2. The cooling temperatures increase the density
3. The more dense material sinks
A convergent boundary forms these types of features (3 examples)
Mountain Ranges, Volcanoes, Earthquakes, Deep-ocean Trenches, Island Arcs, Subduction Zones
How many centimeters is 2300 km?
230,000,000 cm
1 km = 100,000 cm
2300 km x 100,000 cm/km = 230,000,000 cm
First produced evidence to support the theory of continental drift.
Alfred Wegener (1910)
What is a subduction zone and at what type of boundary do they form?
How is a canoe or kayak floating downstream in a river an analogy is an analogy for plate tectonic movement?
Convection currents in the mantle work in a similar way to currents in the river, pulling pieces of lithosphere (canoe) on top of the convection currents of the flowing asthenosphere (river).
Why don't continent-continent convergent boundaries, like the Himalayan Mountains, form deep trenches and volcanoes as we see in ocean-ocean and ocean-continent?
There is no subduction in continent-continent convergent boundaries because continental crust is less dense and doesn't sink back into the mantle.
If a plate moves 10 km in 425,000 years what is the rate of speed of that plate?
2.35 cm/year
S=?
D=10km X 100,000cm/km = 1,000,000 cm
T= 425,000 years
S=D/T
S= 1,000,000cm/425,000years
S= 2.35cm/yr
What were the first 3 pieces of evidence for continental drift and give one example of more recent evidence that has supported sea-floor spreading.
First Evidence Tectonics
1. Geologic Features - Coastlines and Mountain Ranges across continents lined up
2. Fossil Evidence - Fossils across continents lined up
3. Climate - tropical plant fossils in Antarctica, coal seams in North America and Europe
Recent Evidence Sea Floor Spreading
1. Convection Currents providing a mechanism
2. Drilling samples showing increased age in rocks further from mid-ocean ridges and lining up with ages on the other side of divergent boundary
3. Magnetic stripes recording magnetic pole reversals and lining up on the other side of the divergent boundary
What is "ridge push" and where does it occur, what is "slab pull" and where does it occur?
"Ridge push" is the process where newly formed crust pushes older crust outward at a divergent boundary. "Slap pull" is the process where gravity and convection currents pull cooler dense crust down into the mantle at subduction zones.
Why does molten material rise when it is near Earth's core in convection currents? 4 parts
1. Molten material is heated by the energy from the core
2. The added heat energy causes the material to expand
3. As the material expands it becomes less dense
4. Less dense molten material will float in more dense molten material
What type of boundary tried to form here in Minnesota - evidence at Taylors Falls and the North Shore. What was the name of this failed boundary?
Divergent. Called the failed Mid-continent Rift Zone or Keweenawan Rift Zone.
How long would it take a plate traveling at 5 cm/yr to travel all the way around the Earth, 40,000km?
Assuming the same rate of speed, how many times could this plate have traveled around the Earth in its' 4.6 Billion year old history?
800 million years, 800,000,000 years - so it could travel around the Earth 5.75 times!
S=5cm/yr
D=40,000km x 100,000cm/km = 4,000,000,000cm
T=?
S=D/T converts to
T=D/S
T=4,000,000,000cm / 5cm/yr = 800,000,000 years
4,600,000,000 years / 800,000,000 years to go around once = 5.75 times around the world!