Download Tectonic Plate Notes (M)

Tectonic Plate Notes (M)
1. Convection in Earth’s upper Mantle—heat from Earth’s core and the mantle itself cause
convection currents in the upper mantle. This is what causes the tectonic plates to move in
the lithosphere.
Lithosphere-layer right below the crust where the tectonic plates are located. This layer
including the tectonic plates floats on top of the upper mantle.
Earths Crust- top layer of the earth where geographical features such as mountains,
volcanoes, and fault lines are created from tectonic plate movements.
2. Continental Drift— Alfred Wegener’s idea that the continents slowly moved over Earth’s
surface.
Pangaea- name of the supercontinent where all the continents were once connected.
3. Wegener’s hypothesis was that all the continents had once been joined together (Pangaea)
and has since drifted apart. His hypothesis was originally rejected by scientists because of lack
of evidence, but now it is believed he was correct.
He believed this based on 3 types of evidence:
a. Evidence from Landforms fitting together like a puzzle
(South America and Africa)
b. Evidence from Fossils on different continents
c. Evidence from similar climate on different continents
4. Mid-ocean ridge—the longest chain of underwater mountains in the world; curves like
the seam of a baseball along the sea floor, extending into all of Earth’s oceans.
Q: How did scientists map the mid-ocean ridge? Sonar (Harry Hess)
5. At the mid-ocean ridge, molten material rises from the mantle and erupts and hardens at
the surface. The molten material then spreads out, pushing older rock to both sides of the
ridge. The further from the ridge the older the rock.
6. Sea-floor spreading—the process that continually adds new material or crust to the ocean
floor. This discovery was a huge step for supporting continental drift.
7. There are 3 types of evidence of sea-floor spreading:
a. molten material near the mid-ocean ridge had a strange shape, like pillows, which can
only form when molten material cools
b. magnetic stripes
c. drilling samples from the ocean floor found that samples of rocks nearest the midocean ridge were younger than the samples of rock that were farther away
8. The Theory of Plate Tectonics—explains the formation, movement, and subduction of
Earth’s plates. The plates move only one to ten cm per year. There are 3 types of boundaries:
9. Three Plate Boundaries (illustrate each of the following)
a. Transform Boundaries- plates sliding past each other forming fault lines. This
is also where the most frequent earthquakes occur. Earthquakes- Movement along a fault
releases strain energy. When this potential energy is released, it moves outward from the fault in
the form of seismic waves. (San Andres Fault Line, California)


b. Divergent Boundaries- Divide or moving away from each other. This is where
you would find the formation of new crust.

c. Convergent Boundaries- Coming together or colliding plates. When plates of
the same density collide, rather than being subducted, the plates pile into
each other, causing one or both plates to fold up like an accordion. This process
elevates the crust, folds and deforms it heavily, and produces a mountain
range.

*subduction- occurs when 2 plates of different densities collide forcing the
denser plate back into the mantle forming ocean trenches. The plate is also burned
up and produces volcanoes. This usually occurs along coastlines where continental
crust meets oceanic crust.
10. Plate movement can alter Earth systems and produce changes in Earth’s surface such as
faulting, earthquakes, volcanoes, rift valleys, mountain building, trenches and volcanoes- just to
name a few!
11. Rift valleys occur on land along divergent boundaries where the plates separate or are
moving away from one another. (Iceland)
12. Land subsidence occurs when the land surface sinks as a result of geologic processes or
human activities.
13. Trenches- deep, linear, relatively narrow depressions in the sea floor, formed by the
subduction of oceanic plates (where one plate slides beneath the other).
14. Most volcanoes occur along convergent plate boundaries; most are along the edge
(coastline) of the continents. (Ring of Fire)
15. Volcanoes form 2 ways:
a. One way is when 2 oceanic plates collide. This can produce a string of volcanic
islands like the Caribbean Islands.
b. The second way volcanoes can form is when an oceanic plate collides with a
continental plate. The older and denser oceanic plate subducts, or sinks below
the less dense plate. Rock in and above the sinking plate melts, forming chambers
of magma that erupt.
16. Ring of Fire- chains of volcano formation around the pacific plate. Formed by convergent
boundaries by process of subduction.