Geoscience Reference
In-Depth Information
sublimation The process through which water changes
directly from ice to the vapor phase. 140
subsidence The settling or sinking of a surface as a
result of the loss of support from underlying water, soils, or
strata. 400
subsolar point The point on Earth where the Sun angle is
90° and solar radiation strikes the surface most directly at any
given point in time. 45
subtropical High (sTH) Pressure system Band of high air
pressure, calm winds, and clear skies that exists at about 25° to
30° N and S latitude. 118
summer solstice Assuming a Northern Hemisphere sea-
sonal reference, the Summer Solstice occurs on June 20 or
21, when the subsolar point is located at the Tropic of Cancer
(23.5° N). 51
sun angle The angle at which the Sun's rays strike the
Earth's surface at any given point and time. This angle is
high at low latitudes and is progressively less at higher
latitudes. 44
sun-synchronous orbit A slightly inclined polar orbit that
keeps pace with the Sun's westward progress as Earth rotates,
resulting in regular return intervals over every location on
Earth. 34
supercell thunderstorms Large thunderstorms that contain
winds moving in opposing directions and that are associated
with strong winds, lightning, thunder, and sometimes hail and
tornadoes. 184
surface tension The contracting force that occurs when the
water surface meets the air and acts like an elastic skin. 267
synclinal valley A topographic valley that occurs along the
axis of a structural syncline. 346
syncline A concave fold in rock in which rock layers are
bent downward to form a trough. 342
systems theory The examination of interactions involv-
ing energy inputs and outputs that result in predictable
outcomes.
Thunderstorm A brief but intense storm that contains strong
winds, lightning, thunder, and perhaps hail. 172
Tombolo A spit or sandbar that connects an island to the
mainland. 521
Topographic map A map that displays elevation data re-
garding the Earth's surface.
30
The shape and configuration of the Earth's
Topography
surface. 30
Trade winds The primary wind system in the tropics that
flows toward the Intertropical Convergence Zone on the equa-
torial side of the Subtropical High-Pressure System. These
winds flow to the southwest in the Northern Hemisphere and
to the northwest in the Southern Hemisphere. 118
Transform plate margin A plate boundary where opposing
plates move horizontally relative to each other. 338
Transpiration The passage of water from leaf pores to the
atmosphere. 148
Transported parent material Parent material such as glacial
or stream sediments that has recently been deposited and in
which soil forms. 272
Tree line The line that represents the upper limit in moun-
tains and high latitudes where environmental conditions sup-
port the growth of trees. 253
Tributary A stream or river that flows into a larger stream or
river. 412
Tropic of Cancer The line of latitude at 23.5° N where the
subsolar point is located (and Sun angle is thus 90°) on the
Summer Solstice in the Northern Hemisphere. 53
Tropic of Capricorn The line of latitude at 23.5° S where the
subsolar point is located on the Winter Solstice (and Sun angle
is thus 90°) in the Northern Hemisphere. 53
Tropical depression A tropical low-pressure system with
central sustained winds ranging between 20 knots and 34
knots (23 mph and 39 mph). 190
Tropical easterlies Band of easterly winds that exists where
northern and southern trade winds converge. 118
Tropical storm A tropical low-pressure system with maxi-
mum sustained winds between 35 knots and 63 knots (39 mph
and 73 mph). 190
Tropopause The top part of the troposphere, which
is identified by where the air temperature is -57°C
(-70°F). 87
Troposphere The lowermost layer of the atmosphere, which
lies between the Earth's surface and an altitude of about 12 km
(~7.5 mi). 86
Trunk stream The primary stream of a drainage basin. 412
Tsunami A destructive sea wave caused by a disturbance
within the ocean, such as an earthquake, volcanic eruption, or
landslide.
6
T
Talus A pile of rock fragments and boulders that accumu-
lates below a cliff due to rockfall.
382
A small lake that forms within a glacial cirque.
458
Tarn
Temperature inversion A layer of the troposphere in
which the air temperature increases, rather than cools, with
altitude. 87
Temporal lag The difference in time between two
events, such as when peak insolation and peak temperature
occur. 93
Thermohaline circulation The global oceanic circulatory
system that is driven by differences in salinity. 132
Thermosphere The upper layer of the atmosphere, which
occurs between about 80 km and 480 km (~50 mi and 300 mi)
in altitude.
355
U
Ubac slope
88
The slope that faces away from the Sun.
252
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