Pacific Northwest Geography Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Physical Geography

A

ablation - all processes that remove material from a glacier, including melting, evaporation, or calving (formation of icebergs). - the loss of snow and ice from a glacier by melting and evaporation. It is the opposite of accumulation

ablation zone - the region of a glacier where more mass is lost (by melting or evaporation) than gained.

abrasion - mechanical grinding or wearing away of material - the way rocks in rivers or glaciers scrape and erode the rocks they are moving over.

abundance - (ecology) the number of individuals of a species in a given area.

accumulation - all processes that add material to a glacier, including snow, rain, material blown by wind, and avalanches.

accuracy - how close a value, such as a measurement of distance or time, is to being correct.

alpine glacier - Alpine glaciers form when snow that falls on the walls and floors of valleys in high mountain regions accumulates to a great depth. As snow accumulates, it is compressed and changed into ice. When the glacier's depth reaches about 30 m (about 100 ft), the whole mass begins to creep down the valley, continuing as long as enough snow falls at the top. As it reaches lower altitudes, where snowfall is insufficient, the glacier melts. - mountain snow and ice moving down hill.

alluvial soil - refers to the process of water deposition of silt, normally associated with deltas and flood plains of major rivers.

alluvium - material deposited by a river


altitude - vertical distance above a surface, usually the height above sea level.

amphibole - a group of dark, rock-forming minerals that have similar crystal form and composition. Amphiboles include hornblende and actinolite. Amphiboles can be a major component of igneous and metamorphic rocks.

andesite - a dark, fine grained extrusive igneous rock that contains plagioclase, and minerals of biotite, hornblende, and pyroxene as well. Andesite is the extrusive equivalent of diorite. annual - yearly.

archeologist - scientist who studies the material remains (as fossil relics, artifacts, and monuments) of past human life and activities

arete - the ridge between two corries


arid - very dry. Arid describes an area with little rain or precipitation, usually less than 25 centimeters (10 inches) of rainfall annually.

asthenosphere - layer within the Earth. The asthenosphere is part of the upper mantle. The asthenosphere is the ductile zone on which the plates of the lithosphere ride.

atmosphere - the envelope of gases that surrounds a planet. Earth's atmosphere consists of mainly oxygen and nitrogen.

atmospheric circulation - movement within the atmosphere caused by differences in pressure.

atmospheric dust - dust and tiny particles, such as volcanic debris, in suspension in the atmosphere.

atmospheric pressure - the amount of pressure exerted by the atmosphere at a given point (force per unit area). Atmospheric pressure is controlled by the density and temperature of the air. Higher temperature and lower density result in lower atmospheric pressure.

atmospheric sciences - the study of the atmosphere. Analysis of the envelope of gases that surrounds the Earth. Atmospheric studies include meteorology and climatology.

attrition - the way that rocks in rivers are worn down by rubbing against each other


axis - an imaginary line through the center of the Earth, around which the planet rotates.

B

bar - mound of gravel and sand deposited by flowing water basal sliding - movement of a glacier due to sliding or slipping along its base on a layer of water or sediment.

basalt - a dark, fine-grained, igneous rock (mafic extrusive igneous rock) that contains large amounts of plagioclase. Gabbro is the intrusive igneous rock equivalent of basalt. Basalt is the common rock type created at mid-ocean ridges and makes up the upper part of oceanic crust.

bedrock - The solid rock that underlies loose material, such as soil, sand, clay, or gravel.

basement (or bedrock) - general terms for underlying material. "Basement" can refer to hard, (consolidated or lithified) rock that underlies softer, unconsolidated sediment. Bedrock usually means underlying rock.

biology - the study of life.

biotite - a dark-colored mineral that commonly breaks apart in thin sheets because of its crystalline structure. Biotite is a member of the mica group. Biotite is an important mineral in many rock types, including granite, schist, and gneiss.

blizzard - a cold windy storm with winds of at least 56 kilometers per hour (35 miles per hour) and temperatures below -6.7°C (20°F). There may be little snow brought by the blizzard; the high winds pick up snow from the ground and carry it, reducing visibility to less than half a kilometer or about a quarter of a mile.

bottleneck - a narrow route

boulder clay - rocks, sands and gravels deposited by melting ice; also known as till


braided (braided stream) - a type of stream with channels that divide and rejoin often. Braided streams look tangled or interlaced, similar to braided hair. - the spitting of a river into different channels

C

calve - the process of forming an iceberg. Icebergs calve off glaciers that reach a sea or a lake, such as ice shelves and ice tongues.

cataract - waterfall with a single, sheer drop

channel - the deepest part of a river

chemistry - the study of the components, properties, and composition of matter.

circulation - the movement or flow of an object within a larger body. Circulation involves the movement of air masses within the atmosphere or the movement of water masses in the oceans.

cliff - a very steep, vertical, or overhanging face of rock

climate - the average condition of the weather at a place over a period of years

climatology - the study of atmospheric (weather) conditions over periods of time measured in years or longer.

coast line - an area of land and water lying next to a shoreline

coastal plain - landform area, near an ocean, with a local relief under 500 feet.

cobble - a rock fragment between 64 and 256 millimeters in diameter, especially one that has been naturally rounded

cold front - the leading edge of a cold air mass as it moves into an area of warmer air. As a cold front passes through a region, colder air moves in, pushing the warmer air out. Cold air is more dense than warm air, therefore the warm air rises above the cold air.

composition - the make-up of a material, what is in a material.

condensation - the opposite of evaporation. The change from a gas to a liquid.

confluence - a. A flowing together of two or more streams. b. The point of juncture of such streams. c. The combined stream formed by this juncture.

Inside PNW

• Portland is located on the Willamette River near its confluence with the Columbia River.
• Great Falls is a city in north central Montana at the confluence of the Missouri and Sun Rivers.
  Outside PNW
  
• The Panama River in easter S.A., formed in south-central Brazil by the confluence of the Rio Grande and Paranaiba river.
• The river sweeps west, forming part of the border between Paraguay and Argentina, to its confluence with the Paraguy River.

conifer - a tree belonging to the class Gymnospermae. Conifers commonly are evergreen and produce pinecones. Bristlecone Pines and the giant redwoods are examples of conifers.

continental - referring to a large land mass or a continent.

continental crust - A type of crust that forms the upper part of the rigid lithosphere, the outer layer of the Earth. Continental crust is less dense and typically thicker than oceanic crust.

continental drift - see Plate Tectonics

continental glacier - A continental glacier covers almost all of Greenland like a huge glacial blanket more than 2700 m (more than 9000 ft) thick. Underlying rock is exposed only near the seacoast, where the glacier breaks up into tongues of ice resembling valley, or alpine, glaciers. As the glacier meets the ocean, fragments, called icebergs, fall off into the sea. A similar glacier covers the entire Antarctic continent.

continental ice sheet - a mass of ice covering a continent.

continental shelf - the region between the shoreline and the continental slope. The continental shelf has formed by slow deposition of sediment eroded from the continent. The continental shelf has a gentle slope (1°) and is the shallowest portion of the ocean floor. Usually the shelf is in ocean water depths of less than 200 meters (650 feet); in Antarctica the continental shelf averages 500 meters in depth (1640 feet)!

continental slope - the narrow, steep (3° to 6° slope) transition zone between the shallow shelf and the deep ocean floor.

convergence - a region where two or more objects come together. The Antarctic Convergence occurs where two surface water masses meet. Convergent ice flow describes where two ice streams or glaciers flow together.

core - the central zones of the Earth. The outer core extends from 2900 kilometers to 5100 kilometers from Earth's surface and is believed to be of molten material (1800 to 3200 miles). The inner core, from 5100 kilometers to the center of Earth at 6400 kilometers, is believed to be solid (3200 to 4000 miles).

Coriolis effect - moving objects appear to deflect from their anticipated straight-line course. Coriolis effect is a result of the rotation Earth (and an observer's position on it).

corrie - a large hollow near the top of a mountain, caused by glacial erosion


corrosion - the way which rivers use the rocks that they carry to batter the land


cosmic radiation - small, high-energy particles from outer space. Most cosmic radiation is absorbed in Earth's outer atmosphere.

cosmochemistry - the study of the origin, distribution and abundance of elements in the universe.

coulee -Western U.S. A deep gulch or ravine with sloping sides, often dry in summer. -a deep dry canyon that has been formed by water.

counter current - a type of transverse current that flows in the opposite direction to another current.

crag and tail - a hill with one very steep side and a gentle slope on the other side caused by ice flowing around it


crevasse - a deep, almost vertical, crack or split in a glacier. Because crevasses can become covered by blown snow, expeditions crossing ice and snow fields must be careful to avoid them.

cross section - a slice through an object that exposes the interior structure of the object. A cross-section of a layer cake would show layers of cake and layers of frosting. Such a cross-section should be eaten quickly.

crust - the outer-most layer of Earth. The crust is the upper layer of the lithosphere, and is made of continental crust and oceanic crust.

cryosphere - the portion of Earth's surface that is frozen throughout the year.

crystallize - to process of forming solids (crystals) from matter that is in a liquid or gaseous state.

current the swiftest part of a stream.

cyclonic - rotation of a water or air mass. A cyclone is an area of low pressure around which strong winds flow. Cyclonic winds flow counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere (viewed from above).

D

dam - a barrier preventing the flow of water - built across rivers or streams.

deciduous - a tree that has its leaves fall to the ground annually; autumn.

delta - a deposit of sediment that occurs at a river mouth. When a river flows into a lake or the sea, the flow slows. The river no longer is capable of transporting the suspended material it was carrying, so the material is dropped from the flow, or deposited, as a delta. Deltas commonly are triangular in shape with the apex at the river mouth. The top of the delta is at the level of the sea or lake. - an area of alluvium at the mouth of a river when it has split up into distributaries

deposit - material that is carried and then released by a natural agent such as wind, water, or ice. Sand dunes are deposits of sand carried and moved by the by the wind.

deposition - the act of depositing or dropping material from a flow of air or water or ice. Till deposition occurs under the ice sheet. - the dropping of rocks and other materials by e.g. glaciers and rivers

density - mass per unit volume. The density of granite, one of the common continental rocks, is on average 2.7 grams per cubic centimeter. The density of basalt, one of the common oceanic crust rocks is on average 3.0 grams per cubic centimeter.

desert - an area where there is little moisture because precipitation is low and evaporation is high. Precipitation usually is less than 25 centimeters a year (10 inches). Large deserts include widely varying climates such as the Sahara Desert in Northern Africa or the continent of Antarctica.

diorite - a type of intrusive rock with a composition between granite and gabbro. Diorite often contains plagioclase, pyroxene, and amphibole (hornblende). Quartz may occur in diorite. The extrusive igneous rock equivalent in composition to diorite is andesite.

distributary - a branch of a river which flows out from the river


distribution - the arrangement or location of features or objects in an area.

divergence (divergent) - a region where two or more objects move apart. The Antarctic Divergence marks the location where two surface water masses flow in different directions. Divergent ice flow describes where ice streams or glaciers flow apart.

divergent margin (plate tectonics)- plate margin where two or more plates are moving away from each other. More.

diversity - variety of different objects or features or organisms. The variety of species in a given region; the number of different species in a particular place.



drift - speed and direction of an iceberg in the water. Iceberg drift is controlled by the size and shape of the iceberg, wind direction and speed, surface currents in the water, and other factors such as surrounding land and sea ice, and depth of the water.

drumlins - tear-drop shaped hills of glacial sediment and/or rock sculpted by the movement of ice across the features. The tails of the tear-drop shapes point in the direction of glacier movement. - a smooth, half egg-shaped hill formed beneath an ice sheet

duration - the amount of time that something lasts or occurs. The duration of one complete rotation of Earth on it's axis is 24 hours.

dynamic - active or energetic. Also relating to the forces that produce motion in objects.

E

earth - third planet of nine within our solar system.

earthquake - a vibration in Earth's surface caused by the sudden movement of two plates along a fault. Worldwide Earthquake Activity in the Last Seven Days



easterlies - winds that blow from the east. In Antarctica, the polar easterlies blow close to the continent. The polar easterlies help move the ocean surface currents known as the east wind drift.

ecology - the study of the relationship between plants and animals and their environment.

ecosystem - a community of plants and animals and the environment, large or small, in which those plants and animals live.

elevation - the height of an object above a particular reference level, usually the height of an object above sea level. Clark County, WA Elevation

englacial - contained or carried within a glacier. Most rock material is carried subglacially or below the glacier, but some material is carried englacially.

equator - an imaginary circle around Earth that divides Earth in half. The Northern Hemisphere is north of, or "above," the equator and the Southern Hemisphere is south of, or "below," the equator. The equator is the line of 0 degrees latitude. The north pole is at 90 degrees north latitude (90°N) and the south pole is at 90 degrees south latitude (90°S).

equatorial - having to do with, or being near, the equator of the Earth. Equatorial can be used to describe the climate, and commonly refers to high temperatures and humidity with a lot of rain.

equinox - the two times each year when the length of day and night are equal in all places on Earth. There is a spring equinox (vernal equinox, around 21 March) and a fall equinox (autumnal equinox, around 22 September). Equinoxes occur in the orbit (revolution) of Earth around the sun when the sun's rays are perpendicular to the equator. During the winter and summer solstice, Earth's position and tilt of axis relative to the sun causes the sun's rays to strike at an angle to the equator, so the length of time of day light is uneven across the surface of Earth.

era - The longest division of geologic time, made up of one or more periods.

erosion - the wearing away of soil and rocks by e.g. rivers and glaciers


erode - to wear away . Wind, water, and movement of glaciers erode the surface of Earth.

erratic (glacial erratic) - a large rock or boulder carried by a glacier away from its place of origin. - a rock transported by ice and dropped in a different area

escarpment -
- A steep slope in front of a fortification
- A long cliff or steep slope separating two comparatively level or more gently sloping surfaces and resulting from erosion or faulting

esker - a long, narrow, ridge of glacial debris left behind by streams that ran within ice tunnels of a glacier. Eskers are helpful to glacial geologists for reconstructing the size and activity of glaciers of the past. a winding ridge of sand and gravel, deposited by a river under the ice

estuary - an embayment along a coastline where rivers meet the sea. An estuary often contains waters of different salinities. The salinities are very fresh where rivers pour into the estuary, and salinities that are almost marine where the estuary opens to the ocean. Estuaries are very important to the marine ecosystem because they are "nurseries" for the early life stages of many marine animals. Unfortunately, because estuaries often are the emptying point for rivers, they are easily polluted by the chemicals and waste carried by the rivers. - the tidal mouth of a river

evaporation - when a liquid or solid changes into a gas or vapor.

evolution - change with time.

evaporation - the change from a liquid or a solid to a gas. In hot arid places, such as the desert, evaporation rates can be very high. Antarctica also is arid - and solid ice can "evaporate" or turn into a gas.

extinction - the complete disappearance of a plant or animal such that it no longer survives anywhere on Earth. Most dinosaurs became extinct around 65 million years ago.

extrusive igneous rock - rocks formed from molten material that cools or crystallizes at the surface of the Earth. Molten rock can cool slowly if it is within the protective, insulating, layers of Earth. However, molten rock also flows from cracks or fissures in Earth's crust or from volcanoes. This lava (molten rock that reaches Earth's surface) cools quickly in the cooler temperatures of Earth's atmosphere. The quickly cooling rocks do not have time to grow large crystals. Extrusive igneous rocks usually are more fine-grained than intrusive igneous rocks. Extrusive igneous rocks include rhyolites, andesites, and basalts. Volcanic ash (pumice) and glass (obsidian) are types of rapidly cooling extrusive igneous rocks.

F

fan - a feature created by deposition of sediment by streams. Fan formation is similar to delta formation, but deltas describe features created where a stream meets a body of water and the top of the delta is built to the water surface. Fans can form on land, such as outwash fans that form in front of glaciers. Fans also can form where a stream enters a body of water below the surface.

fauna - animals. Antarctic fauna includes seals, penguins, whales, krill, ice fish, mites, and midges (plus a few other animals!).

feldspar - a group of rock-forming minerals that contain aluminum and silica and varying amounts of sodium, potassium, and calcium. Feldspars are the most abundant mineral group and make up 60% of Earth's crust. Feldspars can be white, pink, or clear.

firn - a transitional stage between snow and glacial ice. Firn is a type of snow that has survived a summer melting season and has become more compact than freshly falling snow.

fissure - a long, very deep, narrow opening. Fissures also are called crevasses.

fjord (fiord) - a long, narrow, steep-walled, u-shaped coastal inlet. - a U shaped valley drowned by the sea to become a long, narrow, steep-sided sea inlet. Fjords typically have been excavated by glaciers.

flood - peak flow of water that tops the banks of a stream channel

flood plain - a wide valley, usually in the lower course of a river


flora - plant life. The limited flora on Antarctica includes mosses and a few flowering plants.

flutes - long grooves running parallel to the direction of glacier movement. Flutes are formed at the bottom of a glacier in a number of ways.

foothill - a physical feature located at the base of a mountain range.

foredeepened topography - landward sloping ground. Foredeepened topography is common in areas that have been covered by glaciers because 1) glaciers erode material away and 2) the weight of the glacier pushes the land down. The ground under an ice sheet may be bowl-shaped, with the inner part being deeper than the ground around the glacier edges.

freeze-thaw action - the weathering process that breaks up rocks by the repeated freezing and thawing of water in cracks


frequency - how often something happens. The number of times an event occurs.

friction - resistance to movement when two bodies rub against each other. Friction acts to keep an object from sliding or moving.

front (meteorology) - the boundary between masses of warm and cold air.

furrow - long grooves in till deposits or basement formed at the base of a moving glacier. The furrows run in the direction of the movement of the glacier. Furrows also are called flutes.

G

gabbro - a group of dark, coarse-grained intrusive igneous rocks that contains plagioclase and pyroxene and very little quartz. Gabbros are the intrusive equivalent of basalt. A gabbro may contain olivine.

geochemistry - the study of the distribution and amounts of chemical elements in the systems of Earth, including the layers of the Earth, the oceans and atmosphere, and the cryosphere. Geochemistry includes study of the flow of the chemicals through the systems.

geology - the study of Earth, its history, and the processes that have occurred and are occurring on and within it. Geologists are interested in how the Earth formed, and what processes have been active in the past, and how those processes might be different from those of today.

geologist - a scientist who studies the history of the Earth and its life, especially as recorded in rocks

geographic region - an area with similaar physical characteristics.

geomagnetic pole - the points on Earth's surface where the axes of the Earth's magnetic pole intersect. In the Southern Hemisphere, the south geomagnetic pole is approximately 1160 kilometers (725 miles) north of the south geographic pole

geomorphology - study of landforms and their origin on the surface of Earth and other planets. Geomorphologists are interested in how landforms developed, and how the surface of Earth evolves.

geophysics - the study of the physical properties of Earth as a planet. A geophysicist might study the interior layers of Earth, or the geomagnetic field of Earth, or Earth's gravity field.

gimbals - device that holds an object and keeps it horizontal and free from surrounding motion. The compass on a ship usually is on gimbals to keep the compass needle swinging freely and not pressing against the glass of the compass face.

glacier - a mass of ice, formed by the recrystallization of snow, that flows forward, or has flowed at some time in the past. - a mass of ice flowing down a valley


glacial deposit - sedimentary material carried by the glacier and left behind. Glacial deposits can have many forms, such as eskers, moraines, drumlins.

glacial erosion - wearing down of Earth's surface by glaciers. The rock debris in the bottom of a glacier scrapes and erodes the surface over which the glacier flows. Glaciers also pluck and gouge the surface of the Earth.

glacial geology - study of the features and processes created by masses of ice. Glacial geologists examine present and past glaciations to understand the causes of glaciations.

glacial lobe - A rounded projection, especially a rounded glacial (continental or alpine glacier) projection.

glacial period (ice age, glacial epoch) - recurring periods in Earth's history when the climate was colder and glaciers expanded to cover larger areas of the Earth's surface.

glaciation - the formation, activity, and retreat of glaciers through time. Glaciation of a region refers to the growth of ice over that region. Large parts of the Northern Hemisphere experienced glaciation in the past.

glacier - a large mass of ice, air, water, and rock debris formed at least partially on land. Glaciers are amounts of ice large enough to flow with gravity because of internal deformation. Glaciers include small valley glaciers, ice streams, ice caps, and ice sheets. The term glacier also includes ice shelves if they are fed by glaciers.

glacier terminus - the leading edge of the glacier; the glacier nose. The glacier terminus often has a large amount of glacial debris.

glaciology - the study of the physical and chemical properties of snow and ice. Glaciologists might study the movement of ice sheets, and how ice flows. Glaciologists also study how snow slowly changes to glacier ice.

glaze - a smooth, clear coat of ice.

gradient - the steepness or angle of a slope. Hills can have a steep gradient, particularly if you are trying to climb up one! Gradient also can refer to the change over distance in something.

granite - an intrusive igneous rock that usually has a light color and large crystals. Granites commonly contain high amounts of quartz and feldspar. Micas, such as muscovite and biotite, might also be present. Granites may form from slowly cooling molten materials deep in Earth's crust. The extrusive igneous counterpart to a granite is a rhyolite.

grassland - an area of land covered with grasses.

gravel - round rock fragments larger than the sand

Gulf Stream - a warm, quickly-moving ocean current that originates in the Gulf of Mexico and moves up the U.S. Atlantic coast before moving across the Atlantic to the European coast, where it converges into another ocean current and becomes the North Atlantic Current. The Gulf Stream is a western boundary current.

H

hanging valley - a u-shaped valley that joins the wall of a larger valley, but the smaller valley floor "hangs" above the larger valley floor. Hanging valleys are carved by valley glaciers. When glaciers filled the two valleys, the smaller valley glacier flowed into the larger valley glacier. - a smaller valley which hangs above the main U shaped valley in a glaciated region

head water - the beginning of a river

heat reservoir - an area where heat is absorbed and then distributed to the surroundings slowly. Oceans and large bodies of water act as heat reservoirs. They absorb heat and slowly passes it to the atmosphere. This is one reason that locations near the sea might stay warmer in the winter.

heat source - a region that receives more energy than it loses. The regions around the equator typically are considered heat sources.

heat sink - a region where more heat is lost than is supplied by incoming solar radiation (insolation). The poles generally are considered heat sinks.

hemisphere - one half of a sphere.

highs (high pressure zones) - areas where the atmospheric pressure is higher than the surrounding region. Clear weather often accompanies high pressure systems.

humidity - the amount of moisture or water vapor that is in the air. Humidity can be absolute or relative. Absolute humidity is the actual mass of water per volume of air (grams per cubic meter). Relative humidity is the amount of moisture in the air relative to the amount of moisture the air could hold at that same temperature.

hurricane - a large, tropical cyclonic storm that reaches minimum wind speeds of 119 kilometers per hour (74 miles per hour). Hurricanes can be hundreds of kilometers wide. Hurricanes may be called "typhoons" in the Western Pacific Ocean and "cyclones" in the Indian Ocean.

hydrology - the study of water (in liquid and solid form) and its flow between the atmosphere, the land, and the ocean.

I

ice - water in a solid form. Water becomes a solid below 32* Fahrenheit.

ice age (glacial period, glacial epoch) - recurring periods in Earth's history when the climate was colder and glaciers expanded to cover larger areas of the Earth's surface. - the long, cold period when ice and snow covered most of northern Europe


ice bridge - a road of ice used to cross a frozen river, lake or bay.

ice cap - a large dome-shaped mass of ice that is thick enough to cover all topography underneath it. Ice caps are smaller than ice sheets, usually with an area less than 50,000 square kilometers (19,000 square miles). Ice caps are large enough to deform and flow with gravity and spread outward in all directions.

ice cliff - walls of ice where glaciers meet the sea, such as at the edge of land or the edge of an ice shelf. Ice cliffs occur in areas where drainage of the ice from the continent diverges and slows.

ice rafted debris - material carried by floating ice that eventually melts out of the ice and is deposited on the floor of the sea or a lake.

ice sheet - a large mass of ice that is thick enough to cover the topography under it. Ice sheets are large enough to deform and move with gravity. Ice sheets are larger than ice caps. Ice sheets cover large parts of Greenland and Antarctica. - a large body of moving ice, usually in a lowland area


ice shelf - a large flat-topped sheet of ice that is attached to land along one side and floats in an ocean or lake. More ice is added to the ice shelf from flow of the ice on land and from new snow. Ice is removed from the ice shelf by calving and melting.

iceberg - a large piece of floating ice that has calved, or broken off, a glacier or ice shelf. Icebergs occur in lakes and the ocean and can be quite large.

indigenous - native to an area. Originating in a location. Not exotic. Penguins are indigenous to the Antarctic. Polar bears are indigenous to the Arctic. If polar bears were introduced to Antarctica they would be exotic and the penguins would be very unhappy.

inhabit - to live in a particular location. People inhabit cities.

intrusive igneous rock - rocks formed from molten material that cools or crystallizes slowly within the protective, insulating, layers of Earth. The slowly cooling rocks grow large crystals. Intrusive igneous rocks usually are more coarse-grained than extrusive igneous rocks. Intrusive igneous rocks include granite, diorite, and gabbro, to name a few. Think about magma from within the earth.

irrigation - a man-mad technique of applying water to agricultural crops and other plants.

inversion layer - a layer of air or water in which the trend of a physical property is opposite to that expected. In meteorology, a layer of air in which the temperature is colder at the bottom and warmer at the top. Usually the temperature becomes colder with height above Earth's surface, but a temperature inversion is the opposite. In Antarctica the inversion layer may be only 100 meters (330 feet) thick, but the temperature can change 30°C (54°F) in that 100 meters!

island - a land mass completely surrounded by either salt or fresh water.

island arc - a curving group of volcanic islands parallel to a deep sea trench. Island arcs and the deep sea trench mark the location where oceanic crust is being subducted under oceanic crust. The Aleutian Islands are an island arc.



isthmus

J

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L

M

N

O

P

PLATE TECTONICS/ CONTINENTAL DRIFT Terms A B theory unproven idea continental drift theory that states continents were joined at one time crust thin, outer surface of the earth mantle layer of earth on which crust floats core innermost layer of the earth tectonic plates sections of the crust that move independently rift separation of the earth's crust folding earth's crust buckles in a wavelike pattern fault a break in the earth's crust lava hot molten rock at the earth's surface magma hot molten rock of the mantle earthquake shaking caused by tectonic movement volcano tectonic forces cause the mantle to explode outward Alfred Wegener developed the theory of continental drift San Andreas major system of faults in California Montserrat Caribbean Island evacuated due to a volcano Mt. St. Helens erupted May 18, 1980 in Washington New Madrid site of major earthquakes in 1811-1812 in Missouri ring of fire highly active volcanic area around the Pacific Ocean tsunami large wave caused by earthquakes plateau - - a usually extensive land area having a relatively level surface raised sharply above adjacent land on at least one side - a similar undersea feature - a region of little or no change in a graphic representation payload - a load carried Pleistocene - an epoch of geologic time that extends from 1.6 million years ago to 10,000 years ago. The Pleistocene commonly is called the "ice age" because it is the most recent time in Earth's history when the climate cooled and glaciers expanded world-wide. physical landscape - the natural scenery of an area Pliocene - an epoch of geologic time that extends from 5.2 million years ago to 1.6 million years ago. The Pliocene closes the Tertiary Period (65 million years ago to 1.6 million years ago). plucking - a form of glacial erosion. While a glacier travels over a bedrock or basement bump in the landscape, it breaks pieces of rock from the bump and carries them down stream. - the way by which moving ice pulls away rocks onto which it has frozen polar - having to do with the regions of the north and or south poles of Earth. The poles are areas of high latitudes and typically are cold, icy regions. A polar climate is a cold climate, with temperatures less than 10°C (50°F). pothole - a circular hole formed in the rocky bed of a river by the grinding action of stones or gravel whirled round by the water precipitation - the transfer of moisture from the atmosphere to the surface of Earth, usually as rain, snow, and ice. The amount of precipitation is always measured as water or rain. Snow fall usually is reported as water-equivalent. pressure melting point - the temperature at which a solid melts changes with changes in pressure. With increasing pressure, the temperature of melting is lowered. The pressure melting point is important to ice movement because the addition of a little water at the base of an ice sheet can greatly increase the rate of the flow of ice. proglacial - the area and features in front of a glacier. pyramidal peak - a pyramid shaped peak made by glacial erosion Q quartz - a typically clear, hard mineral that is very common in igneous, metamorphic, and sedimentary rocks. R radiocarbon dating - an absolute dating method used to measure the age of organic matter (bone, shell, wood). Radiocarbon dating involves measuring the relative amounts of carbon isotopes in a sample. Radiocarbon dating can age date materials that formed approximately 50,000 years ago or less. raft - to transport rainshadow region - A part of the earth characterized by distinctive landforms, animal or plant life. reservoir - an artificial lake where water is collected and kept in quantity for use - a manmaade lake, usually behind a hydroelectric dam, with the primary purpose of storing water for use later in the year. rhyolite - an extrusive igneous rock that usually has a light color and is very fine grained (small crystals). Rhyolites commonly contain high amounts of silica, with quartz and feldspar crystals. The fine-grained nature is a result of rapid cooling at the surface of Earth. Rhyolites may originate from volcanic eruptions. The intrusive igneous counterpart to a rhyolite is a granite. ridge - a long, narrow feature that is higher than the geography surrounding it. The mid-ocean ridge is a large ridge on the ocean floor. Eskers are ridges that trace the path of meltwater tunnels in glaciers. Esker ridges are MUCH smaller than mid-ocean ridges! ripple marks - deposits of sediment that have been left by fast-moving water in the shape of parallel, long rows river - a natural stream of water of usually considerable volume river beach - a build up of material deposited in the inside bend of a river river cliff - the steep bank made by erosion on the outside bend of a river river terrace - a flat bench lying on each side of a river valley roche moutonee - a large rock smoothed by ice on its upstream side, jagged on its downstream side rock flour - very fine particles of sediment that result from glacial scouring and grinding of rock material as the glacier moves. Rock flour is carried at the base of glaciers and also by meltwater. Lakes in glaciated areas often have a milky turquoise color because of the suspended rock flour in the water. rookery - a colony of penguins or seals. S salinity - the amount of dissolved salts contained in sea water. The average salinity of sea water is 35 parts per thousand. Freshwater has a salinity of 0 parts per thousand. scabland - an irregular surface of land shaped by floodwaters with exposed lava rocks and a thin layer of soil and sparse vegetation scree - a pile of loose jagged rocks made by freeze-thaw sediment - matter that settles to the bottom of a liquid sedimentary rocks - Think sand stuck together. sedimentation - Solid fragments of inorganic or organic material that come from the weathering of rock and are carried and deposited by wind, water, or ice. silt - loose sedimentary material with rock particles usually 1/20 millimeter or less in diameter soil- the upper layer of earth that may be dug or plowed and in which plants grow scour - to remove or sweep away material. Glaciers scour the landscape and fast-moving ocean currents scour the sea floor. sea ice - a general term for the seasonal ice that forms from seawater. Sea ice can cover large parts of polar waters in the winter. The sea ice melts back in the summer. sediment - unconsolidated particles, ranging from clay-size to boulders that may be carried by natural agents (wind, water, and ice) and eventually deposited to form sedimentary deposits. Organisms and chemical precipitation also can produce sediment. Sediment is produced by the breakdown of rocks. sedimentary rocks- a rock formed by the consolidation or cementation of sediment particles. shoreline - the region where land and a body of water meet. source - the start of a river Southern Hemisphere - the southern half of the Earth. The part of the globe "below" the equator. south geographic pole - 90°S. The south geographic pole is the southern location where the axis of rotation of Earth intersects Earth's surface. It also is home to Amundsen Scott Station. south magnetic pole - the point on Earth's surface that a south-seeking compass needle seeks. This point is off the coast of Wilkes Land. sphere - a round, globular shape. A basketball, baseball, and the Earth, moon, and sun are spheres. spur - a ridge of rock which juts down into a valley strata - actual layers of sedimentary rocks. The layers might contain differences in texture, color, fossil content, or material type. stratopause - a layer within the atmosphere occurring 50 kilometers above Earth's surface (31 miles). The stratopause is the boundary between the stratosphere and the overlying mesosphere. stratosphere - the layer of the atmosphere that is above the troposphere. The stratosphere extends from approximately 10 to 50 kilometers (6 to 31 miles) above Earth's surface. It contains ozone in its upper layers. subduction (plate tectonics) - the process of oceanic lithosphere moving beneath another plate at a convergent (colliding) margin. subglacial - under the glacier. T tectonic - relating to the forces and the movements of Earth and its crust. Earthquakes, volcanoes, and mountain building are related to tectonic activity. temperate - mild or moderate. The middle latitudes, between tropical and polar climate regimes, is generalized as a temperate climate. More. temperature - the degree of heat or cold. terminal moraine - an accumulation of glacial debris that occurs at the nose or snout of a glacier. The debris has been carried at the base or, within, or on top of the glacier. A terminal moraine marks the maximum extent of the glacier's advance. - moraine deposited at the end of a glacier terrestrial - land above sea level. Terrestrial flora and fauna live within land-based environments, not within the aquatic realm. Giraffes are an example of terrestrial fauna. till - sediment deposited by a glacier. Till usually is not sorted; it contains many sizes of sediment. Till usually is not stratified (layered). topography - the configuration of a surface including its relief and the position of its natural and human-made features topsoil - surface soil usually including the organic layer in which plants have most of their roots and which the farmer turns over in plowing topography - surface relief of the land. Topography usually is measured in meters above sea level. The topography can be very different from one location to another. Topography can be flat, or mountainous, or hilly. trade winds - one of the three major circulation cells in the each hemisphere. The trade winds from approximately 0° to 30° north or south latitude. Within the regions of the trade winds, prevailing winds blow toward the west. transportation - the carrying of rock particles trench - a long, narrow, deep, steep-sided depression on the sea floor. tributary - a stream that flows into or joins a larger stream. - a smaller river which flows into a larger one a larger glacier. Also used to describe a small glacier flowing into a larger glacier. ex. The Snake River is the largest tributary of the Columbia River. trough - a channel or trench. A linear depression in the landscape or in sea floor bathymetry. truncated spur - a spur that has been truncated, or cut off, by moving ice U upper course of a river - the first part of a river U-shaped valley - one that has steep sides and a flat bottom and has been overdeepend by a glacier V V-shaped valley - a valley that has been eroded by a river valley glacier (alpine glacier) - a glacier flowing within the walls of a mountain valley. volcanic rocks - Think about lava flowing outside the inner earth. W warm front - the leading edge of a warm air mass as it moves into an area of colder air. As a cold front passes through a region, warmer air moves in, pushing the cold air out. Warm fronts usually bring precipitation. weathering - the process by which rocks are worn away but not transported away. West Wind Drift (Antarctic Circumpolar Current) - a Southern Ocean surface current that flows to the east and is driven by westerly winds. The West Wind Drift carries a large volume of water and it is a strong current because no continents are in the way of the flow path. westerlies - winds that blow from the west. whalebacks - elongated mounds or hills shaped by glacier movement. Whalebacks may indicate direction of the ice flow. Whalebacks are smaller than drumlins and roches moutonnees. The shape of whalebacks looks similar to...guess what?! BR> white-out - a weather condition in which the horizon cannot be identified and there are no shadows. The clouds in the sky and the white snow on the ground blend. White out conditions are potentially dangerous because it is difficult to find a point of reference. wind chill - an expression of temperature that incorporates wind speed in the temperature reported. Wind can make the temperature feel cooler. The wind chill factor is a way of expressing how cold the wind might make the temperature feel. X X-ray - electromagnetic radiation of very short wavelength. The wavelengths of X-rays are shorter than ultraviolet radiation (which are of shorter wavelength than visible light). Y Z zero population growth the point at which there is no increase in popumation. Zero population growth occurs when the birth rate and death rate are approximately the same. zeugen a pedestal rock with tabular shaped profile caused by wind erosion. Examples can be seen in most deserts, but especially in Central Asia. zone of transition an area of changing land-use between two zones. zonal Soil a soil found in large areas having a similar climate and vegetation. zooplankton - microscopic free-swimming or suspended marine or freshwater animals within the planktonic or planktic community. Many organisms spend part of their lives as zooplankton, either in a juvenile life stage or an adult life stage (including crustaceans like shrimp, echinoderms or starfish, corals). Back to the top Back to the top Back to the top