Exam 2 Review Flashcards
(51 cards)
Pahoehoe
basaltic lava forming smooth undulating or ropy masses.
Viscosity
the state of being thick, sticky, and semifluid in consistency, due to internal friction.
Flood basalts
A flood basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava.
Erupting column
cloud of hot volcanic ash suspended in volcanic gas emitted during an explosive volcanic eruption
Gas thrust region
At the base of the column, material is forced upwards out of the vent by the pressure of expanding gas, mainly steam. The gas expands because the pressure of rock above it rapidly reduces as it approaches the surface
Convective region
covers most of the height of the column. The gas thrust region is very turbulent and surrounding air becomes mixed into it and heated. The air expands, reducing its density and rising. The rising air carries the solid and liquid material from the eruption entrained in it upwards.
Umbrella region
As the column rises into less dense surrounding air, it will eventually reach an altitude where the hot, rising air is of the same density as the surrounding cooler air. In this neutral buoyancy region, the erupted material will then no longer rise through convection, but solely through any upward momentum which it has
Liquifaction
describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid.
Hypsometric curve
histogram or cumulative distribution function of elevations in a geographical area. Differences in hypsometric curves between landscapes arise because the geomorphic processes that shape the landscape may be different.
Isostasy
the equilibrium that exists between parts of the earth’s crust, which behaves as if it consists of blocks floating on the underlying mantle, rising if material (such as an ice cap) is removed and sinking if material is deposited.
Craton
A portion of a continental plate that has been relatively undisturbed since the Precambrian Era.
shield
exposed part of the craton
platform
covered part of the craton
active margin
found on the leading edge of the continent where it is crashing into an oceanic plate
passive margin
transition between oceanic and continental lithosphere that is not an active plate margin.
lithosphere
0-100km
low velocity zone
100-200km
partial melt in asthenosphere
upper mantle
0-400km
between 200-400km, atoms pack more tightly
transition zone
400-600km
olivine transforms to spinel structure and to perovskite structure
lower mantle
600km-100km
layers of ocean crust
sediment pillow basalt dikes gabbro lithosphere mantle
hot spot
volcanic surface expression of a mantle plum
mantle plume
– very hot, thin, cylinders of rising mantle
– may originate at the core mantle boundary
rifting
Inception of rifting along the East African rift system
