Plate Tectonics/Volcano Study Guide
o Continental Drift- Wegener searched for evidence supporting his hypothesis. Name 3 of
the following:
o Matching Coastlines
o Matching Mountain Ranges
o Glacier Evidence
o Fossil Evidence-Mesosaurus
o Drifting continents explained dramatic climate changes on some continents
o Tropical plant fossils- (coal) in frozen Antarctica
o Tropical fern fossils (Glossopteris) in now colder climates
o Glacier deposits in South Africa
o Polar dinosaurs found in Australia
o Paleomagnetism- The magnetic pattern created a striped appearance when mapped
- The pattern was a mirror image on either side of mid-ocean ridge
-Seafloor spreading
- Ages of rocks near mid-ocean ridges was youngest
- Age increased away from ridge
- Age of rocks with same magnetism is same
- If the new crust is formed at mid-ocean ridges, why isn’t earth getting larger?
Answer: it is being subducted and recycled into the mantle at ocean trenches at
convergent boundaries
-Earthquakes
-Earthquakes are concentrated a plate boundaries
-Plate Tectonics
- The lithosphere is made up of about 20 plates which move relative to each other in
several ways
-3 Types of Boundaries
- 1. Convergent- where plates come together
-2. Divergent- Found at spreading centers- either mid-ocean ridges or mid –continental
rift zones
-3. Transform fault boundary (San Andreas Fault)- It is a transform fault boundary,
where the the plates move sideways each other.
- Plate Tectonic Clauses
- Volcanic activity
-Earthquakes
- It causes rocks to be tilted
-To fold or break
- Weather and erosion tear structures down while, Plate tectonics builds them up
- Isostasy- is balance
- As plate motions push it higher the mountain sinks into the mantle to stay in balance.
- When the mountain erodes, it will rise in the mantle as the top erodes
A .Occurs where plates pull apart, divergent boundaries, and is called tension
B. Occurs where plates converge, and is called compression
c. Occurs where plates move past each other, at transform fault boundaries and is called
shearing
- Strain
- If it is warm underground, it can bend
- The rock may break if it is brittle
Normal Fault
Strike Slip Fault
Reversse Fault
-Volcanoes
-Romans believed in Vulcan, god of fire
- Hawaiians believed in Pele, goddess of fire
-Definitions
-Magma- melted or molten rock beneath the surface of the earth
- Lava- when magma pours forth on the surface of the earth
-Volcanic eruption- when magma pushes its way up through cracks, holes or tubes
- A volcano can be 2 things
- A hole in the ground that lava comes through
- A hill or mountain formed by lava
-Hot Spots- Develop over a mantle plume and as the plates move over and magma builds up
volcanic islands are created
- Shield Volcanoes
- Shaped like an ancient warriors shield
- volcanoes with broad, gentle slopes and built by the eruption of fluid basalt lava
- Cinder Cone Volcanoes
-Simplest type of volcano
- they erupt explosively, blowing out burning ashes and cinders. The ashes and cinders
build up to form the cone shape
-Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a
thousand feet or so above their surroundings
-Composite Volcanoes
- Symmetrical cones of large dimension built of alternating layers of lava flows, volcanic
ash, cinders,blocks and bombs
- they may rise as much as 8,000 feet above their bases
- Types of flows of Volcanic Volcanoes
-AA- thick, slow moving that hardens into rough tangle of sharp rocks
- Pahoehoe- thin, hot quick moving lava that forms smooth, billowy surface
Extra Credit: Name the popular volcanoes we discussed in class and in your notes