KEY TERMS Flashcards
abyssal plains
very flat areas that make up most of the ocean floor
bathymetric map
a map of the seafloor created from the measurement of water depths.
continental arc
a line of volcanoes sitting on a continental plate and aligned above a subducting oceanic plate near a deep sea trench.
continental drift
the hypothesis developed in the early 20th century that states that the continents move about on the surface.
convergent plate boundary
a location where two lithospheric plates come together
divergent plate boundary:
a location where two lithospheric plates spread apart.
echo sounder
a device that uses sound waves to measure the depth to the seafloor.
epicenter
he point on the Earth’s surface directly above an earthquake’s focus, which is the place where the ground breaks.
fault
a fracture along which there has been movement of rock on one or both sides
hotspot
plume of hot material that rises through the mantle and can cause volcanoes
intraplate activity
geologic activity such as volcanic eruptions and earthquakes that takes place away from plate boundaries.
magnetometer
instrument that measures the intensity of a magnetic field
mid-ocean ridge:
the location on the seafloor where magma upwells and new seafloor forms. Mid-ocean ridges are the dominant feature of divergent plate boundaries found in the oceans.
Pangaea
in early geologic time, a supercontinent that incorporated almost all the landmasses on Earth.
plate
a slab of the earth’s lithosphere that can move around on the planet’s surface.
plate boundary
a location where two plates interact.
plate tectonics
the theory that the Earth’s surface is divided into lithospheric plates that move on the planet’s surface. The driving force behind plate tectonics is mantle convection.
seafloor spreading
the mechanism for moving continents. The formation of new seafloor at spreading ridges pushes lithospheric plates on the Earth’s surface.
subduction
the sinking of one lithospheric plate beneath another.
subduction zone
the area where two lithospheric plates come together and one sinks beneath the other.
transform plate boundary
the type of plate boundary where two plates slide past one another.
trench
a deep hole in the seafloor where subduction takes place. Trenches are the deepest places on Earth.
anticline
A fold that arches upward, in which the older rocks are in the center and the younger rocks are at the outside.
compression
Stresses that push toward each other. This causes a decrease in the space a rock takes up.
confining stress:
The stress due to the weight of material above a buried object. Confining stress reduces volume but causes no deformation.
deformation
The change of shape that a rock undergoes when it has been altered by stresses. Also called strain.
elastic deformation
A strain that temporarily alters the shape of rocks.
elastic rebound theory
The theory that earthquakes occur when rocks break and snap back to their original position after being deformed elastically until they cannot deform anymore.
epicenter
The point on the earth’s surface that lies above an earthquake’s focus
fault zone
A network of related faults.
fracture
Cracks or breaks in rocks caused by stress.
focus
he point where rocks rupture during an earthquake.
fold
A bend in a set of rocks caused by compression
joint
A break in rock caused by stresses along which there is no movement.
liquefaction
Clay, silt, and sand saturated with water become like quicksand, lose their strength and behave more like a liquid than a solid.
Mercalli intensity scale
This scale measures the effects of earthquakes seen on the land surface and felt by humans. It measures from I-XII.
moment magnitude scale
This is a logarithmic scale that measures the total energy released by an earthquake. An increase of one integer indicates a 30-fold increase in energy released. An increase of two integers indicates a 1,000-fold increase in energy released.
monocline:
A bend in a set of rocks that causes them to be inclined relative to the horizontal.
normal fault:
A fault in which the rocks above the fault plane, or hanging wall, move down relative to the rocks below the fault plane.
plastic deformation:
A strain that permanently alters the shape of rocks.
primary waves (P-waves)
P-waves are body waves that are the first to arrive at a seismometer because they are the fastest. P-waves are longitudinal waves that travel through solids, liquids, and gases.
retrofitting:
