Download Dynamic Earth Unit 4 Study Guide Ans. key

Dynamic Earth Unit 4 Study Guide

What is continental drift?
a. Hypothesis where continents were once a single landmass that broke apart and drifted to
their present locations.

What is slab pull?
a. Process of slow plate movement that occurs in the mantle below a convergent plate
boundary when a denser plate sinks beneath another less dense plate.

What is ridge push?
a. Force which pushes cooling dense plates down the slope of the asthenosphere away from
mid-ocean ridges.

What is mantle convection?
a. Movement of material in the mantle due to differences in density.

What kind of landform can be created at convergent boundaries?
a. Mountains

Compare the densities of oceanic and continental crust.
a. Oceanic crust is denser than continental crust.

Compare the thicknesses of oceanic and continental crust.
a. Continental crust is thicker than oceanic crust.

What happens to the tectonic plates at each type of boundary?
a. At divergent boundaries, plates separate, at convergent boundaries, plates move toward
each other, and at transform boundaries, plates slide past each other.

Compare the three types of faults.
a. In a strike-slip fault, fault blocks move past each other horizontally, in a normal fault,
hanging wall moves down relative to the footwall, and in a reverse fault, hanging wall moves
up relative to the footwall.

What is deformation?
a. Process by which rock changes shape under stress.

Compare the three types of stress.
a. Shear stress causes deformation by pushing rock in parallel but opposite directions and
leads to earthquakes at transform boundaries, Tension causes deformation by stretching or
pulling rock apart and leads to fault-block mountains forming, and compression causes
deformation by squeezing rock together and forms mountain ranges. Compression can also
lead to reverse faults forming which can lead to strong earthquakes occuring at convergent
boundaries.

What types of stress is associated with each type of tectonic boundary?
a. Shear stress is found along transform boundaries, Tension is found along divergent
boundaries, and Compression is found along convergent boundaries.

Compare anticlines and synclines.
a. An anticline is folding in which the oldest layers of rock are found at the core and a syncline
is folding in which the youngest layers of rock are found at the core.

What are the three types of mountains?
a. Folded mountains form when rock is squeezed together at convergent boundaries, Volcanic
mountains form when melted rock erupts onto Earth’s surface at convergent boundaries,
and Fault-Block mountains form when tension makes the lithosphere break into many
normal faults.

What are volcanic vents?
a. Volcanic vents are openings in volcanoes where magma can erupt onto Earth’s surface.

What is a volcanic crater?
a. A volcanic crater is a small depression that forms around the volcano’s vent.

What is magma?
a. Magma is molten rock that is found below Earth’s surface.

What is the difference between magma and lava?
a. Magma is found below Earth’s surface and lava is found above Earth’s surface.

What is a mantle plume?
a. Mantle plume is a column of extremely hot mantle rock that is found beneath a hot spot.

What is a hot spot?
a. A hot spot is a volcanically active area of Earth’s surface.

What is pyroclastic material?
a. Pyroclastic material is hot ash and bits of rock that is ONLY associated with explosive
volcanic eruptions.

What is the difference between the epicenter and the focus of an earthquake?
a. The focus is a place within Earth along a fault at which the first motion of an earthquake
occurs. The epicenter is the position on Earth’s surface directly above the focus.

How does distance from an epicenter affect the strength of an earthquake?
a. The strongest effects are found at the epicenter and decrease the farther an area is located
away from the epicenter.

How are earthquakes associated with plate boundaries?
a. Earthquakes take place where the motion of tectonic plates transfers energy to rock.

What is a tsunami, how are they formed?
a. A tsunami is a series of extremely long waves that can travel across the ocean at very high
speeds. It forms when an earthquake occurs beneath the ocean.

What is the difference between body waves and surface waves?
a. Body waves travel outward from the focus through the interior of Earth, while surface
waves travel only on the surface.

How do P waves and S waves travel through rock?
a. P waves move through rock by compression and expansion of rock parallel to the direction
the wave is traveling and S waves move rock from side to side.

What factors can increase the damage caused by an earthquake?
a. Some factors that can increase the damage caused by earthquakes are the magnitude or
amount of energy released at the focus, sediments that contain water, and a shallower
depth of the earthquake’s focus.

How many times stronger is the ground motion for each unit increased on the Richter scale?
a. The ground motion is 10 times stronger for each unit increased on the Richter scale. For
example, an earthquake with a magnitude of 5.0 on the Richter scale produces 10 times as
much ground motion as an earthquake with a magnitude of 4.0.