Exam 3 Review.

In the theory of Plate Tectonics, the initial, large landmass is called:
The breakup of Pangea occurred approximately how many years ago?
225 million.
What is some evidence that supports the theory of plate tectonics?
Reversal of magnetic fields, seafloor spreading, and the fossil record.
What are the "plates" of plate tectonics made up of?
Where is new lithosphere created?
Divergent plate boundaries
At what type of plate boundary do the deepest earthquakes occur?
What type of plate boundary is parallel to the direction of plate movement?
Transform plate boundaries.
How old are the oldest rocks on the ocean floor?
About 200 million years old.
Tectonic plates move because ___.
The plates are the upper parts of large, deep mantle convection cells.
A mantle plume is ___.
A rising column of hot plastic mantle rock.
Shallow, intermediate and deep focus earthquakes occur at ___.
Convergent plate boundaries.
What type of seismic wave causes the most building damage?
Surface waves
Shallow earthquakes, less than 20 km deep, are associated with ____.
convergent, transform, and divergent plate boundaries.
Which of the following types of seismic waves arrive at a seismograph first?
P waves.
An earthquake's Richter magnitude is based on ____.
The amount of ground movement caused by seismic waves.
What does the elastic rebound theory describe?
The build-up and release of stress during an earthquake.
Energy waves that are released during an earthquake are called ___.
Seismic waves.
Which of the following statements best describes the current state of earthquake prediction?
Scientists cannot yet accurately predict most earthquakes.
How do rock particles move during the passage of an S wave through the rock?
Back and forth at right angles to the direction of wave travel.
The modified Mercalli intensity scale measures ____.
The amount of destruction caused by an earthquake.
A cool rock near the Earth's surface is more likely to ___ than a similar rock that is hot and under great pressure.
Undergo brittle fracture.
A fold in a rock indicates what?
The rock has deformed in a plastic manner.
A fold ___.
Usually results from compressive stress, always shortens the horizontal distances in rock, and usually occurs as part of a group of many similar folds.
A syncline ___.
Is the portion of a fold that arches downward.
Where two oceanic plates converge, one sinks beneath the other and dives into the mantle forming what?
An island arc.
The Himalayas were formed ___.
By convergence of two plates carrying continental crust.
What determines the slope of a cinder cone?
The maximum angle at which cinders remain stable.
What type of volcano consists of both lava flows and pyroclastic deposits?
A stratovolcano
Yellowstone is an example of a ___.
Over the past 2,000 years, which of the following volcanic hazards has caused the most fatalities?
Pyroclastic flows
How can volcanic eruptions endanger commercial air traffic?
Volcanic ash lofted into the air can damage engines.
Eruptions of rhyolite lava tend to be more explosive than basaltic and andesitic lavas because
Rhyolite lavas contain more gases.
Which of the following processes causes melting of the asthenosphere and the generation of magma?
Decreasing pressure.
Which of the following tectonic environments does not generate large quantities of magma?
Transform boundaries.
The magma type that most commonly rises to the Earth's surface to erupt from a volcano is ___.
Basaltic magma.
Pyroclastic bombs, cinders, and ash ___.
Erupt explosively from volcanoes.
A caldera is a ___.
Circular depression formed as the roof of a magma chamber collapses during an eruption.
Geologists use what to determine the relative ages in a rock sequence?
Cross-cutting relations, fossils, stratigraphy.
The principle of cross cutting features states that ____.
A fault is younger than the rocks it cuts.
The law of Uniformitarianism states that:
Natural processes operating today are the same as those that prevailed in the geological past.
Which of the following is the best statement of the principle of original horizontality?
Sediments are deposited as horizontal layers.
The principle of superposition states that ___.
Undisturbed sedimentary layers get progressively younger from bottom to top.
What is an unconformity?
A gap in the geologic record.
A nonconformity is:
An unconformity between two very different rock types.
The last era of Phanerozoic is ___.
The second to last era of Phanerozoic is ___.
The first era of Phanerozoic is ___.
Relative age measurement refers to ___.
The order in which events occur.
A geologist uses radiometric dating to identify ___.
Absolute time.
Parent and daughter isotopes occur when the isotope is ___.
Nonstable and radioactive.