| A | B |
|---|
| abrasion | the grinding away of rock by other rock particles carried in water, ice, or wind |
| absolute age | the age of a rock given as the number of years since the rock formed |
| alluvial fan | a wide sloping deposit of sediment formed where a stream leaves a mountain range |
| amphibian | a vertebrate that lives part of its life on land and part of its life in water |
| atmosphere | the mixture of gases that surrounds Earth; the outermost of the four spheres into which scientists divide Earth |
| atom | the smallest particle of an element |
| beach | wave-washed sediment along a coast |
| bedrock | the solid layer of rock beneath the soil |
| biosphere | all living things; one of the four spheres into which scientists divide Earth |
| carbon film | a type of fossil consisting of an extremely thin coating of carbon on rock |
| cast | a fossil that is a copy of an organism's shape, formed when minerals seep into a mold |
| chemical weathering | the process that breaks down rock through chemical change |
| conservation plowing | soil conservation method in which the dead stalks from the previous year's crop are left in the ground to hold the soil in place |
| continental glacier | a glacier that covers much of a continent of large island |
| contour interval | the difference in elevation from one contour line to the next |
| contour line | a line on a topographic map that connects points of equal elevation |
| contour plowing | plowing fields along the curves of a slope to prevent soil loss |
| controlled experiment | an experiment in which all factors except one are kept constant |
| decomposer | soil organism that breaks down the remains of organisms and digests them |
| deflation | wind erosion that removes surface materials |
| degree | a unit used to measure distances around a circle. One degree equals 1/360 of a full circle |
| delta | a landform made of sediment that is deposited where a river flows into an ocean or a lake |
| deposition | process in which sediment is laid down in new locations |
| digitizing | converting information to numbers for use by a computer |
| divide | the ridge of land that separates one drainage basin from another |
| drainage basin | the land area from which a river and its tributaries collect their water |
| Dust Bowl | the area of the Great Plains where wind erosion caused soil loss during the 1930s |
| element | a type of matter in which all the atoms are the same |
| elevation | height above sea level |
| energy | the ability to do work or cause change |
| epochs | subdivisions of the periods of the geologic time scale |
| equator | an imaginary line that circles Earth halfway between the North and South poles |
| era | one of the three long units of geologic time between the Precambrian and the present |
| erosion | the process by which water, ice, wind, or gravity moves weathered rock and soil |
| evolution | the process by which all the different kinds of living things have changed over time |
| extinct | describes a type of organism that no longer exists anywhere on Earth |
| extrusion | an igneous rock layer formed when lava flows onto Earth's surface and hardens |
| fault | a break or crack in Earth's lithosphere along which the rocks move |
| flood plain | wide valley through which a river flows |
| fossil | the preserved remains or traces of living things |
| friction | the force that opposes the motion of one surface as it moves across another surface |
| geologic time scale | a record of geologic events and life forms in Earth's history |
| glacier | a large mass of moving ice and snow on land |
| Global Positioning System | a method of finding latitude and longitude using satellites |
| globe | a sphere that represents Earth's surface |
| groundwater | water that fills the cracks and spaces in underground soil and rock layers |
| gully | a large channel in soil formed by erosion |
| half-life | the time it takes for half of the atoms of a radioactive element to decay |
| hemisphere | one half of the sphere that makes up Earth's surface |
| humus | dark-colored organic material in soil |
| hydrosphere | Earth's water and ice; one of the four spheres into which scientists divide Earth |
| hypothesis | a prediction about the outcome of an experiment |
| ice age | one time in the past when continental glaciers covered large parts of Earth's surface |
| ice wedging | process that splits rock when water seeps into cracks, then freezes and expands |
| index fossils | fossils of widely distributed organisms that lived during only one short period |
| intrusion | an igneous rock layer formed when magma hardens beneath Earth's surface |
| invertebrate | an animal without a backbone |
| karst topography | a type of landscape in rainy regions where there is limestone near the surace, characterized by caverns, sinkholes, and valleys |
| kettle | a small depression that forms when a chunk of ice is left in glacial till |
| key | a list of the symbols used on a map |
| kinetic energy | the energy an object has due to its motion |
| landform region | a large area of land where the topography is similar |
| landform | a feature of topography formed by the processes that shape Earth's surface |
| latitude | the distance in degrees north or south of the equator |
| law of superposition | the geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it |
| lithosphere | Earth's solid rock outer layer. One of four spheres into which scientists divide Earth |
| litter | the loose layer of dead plant leaves and stems on the surface of the soil |
| load | the amount of sediment that a river or stream carries |
| loam | rich, fertile soil that is made up of about equal parts of clay, sand, and silt |
| loess | a wind-formed deposit made of fine particles of clay and silt |
| longitude | the distance in degrees east or west of the prime meridian |
| longshore drift | the movement of water and sediment down a beach caused by waves coming in to shore at an angle |
| mammal | a warm-blooded vertebrate that feeds its young milk |
| manipulated variable | the one factor that a scientist changes during an experiment |
| map projection | a framework of lines that helps to show landmasses on a flat surface |
| map | a model of all or part of Earth's surface as seen from above |
| mass extinction | when many types of living things become extinct at the same time |
| mass movement | any one of several processes by which gravity moves sediment downhill |
| meander | a looplike bend in the course of a river |
| mechanical weathering | the type of weathering in which rock is physically broken into smaller pieces |
| mold | a fossil formed when an organism buried in sediment dissolves, leaving a hollow area |
| moraine | a ridge formed by the till deposited at the edge of a glacier |
| mountain | a landform with high elevation and high relief |
| mountain range | a series of mountains that have the same general shape and structure |
| operational definition | a statement that describe how to define or measure a particular variable |
| oxbow lake | a meander cut off from a river |
| paleontologist | a scientist who studies fossils to learn about organisms that lived long ago |
| period | one of the units of geologic time into which geologists divide eras |
| permeable | characteristics of a material that is full of tiny, connected air spaces that water can seep through |
| petrified fossil | a fossil in which minerals replace all or part of an organism |
| pixels | the tiny dots in a satellite image |
| plain | a landform made up of flat or gently rolling land with low relief |
| plateau | a landform that has high elevation and a more or less level surface |
| plucking | the process by which a glacier picks up rocks as it flows over the land |
| potential energy | energy that is stored and available to be used later |
| prime meridian | the line that makes a half circle from the North Pole to the South Pole and that passes through Greenwich, England |
| radioactive decay | the breakdown of a radioactive element, releasing particles and energy |
| relative age | the age of a rock compared to the ages of rock layers |
| relief | the difference in elevation between the highest and lowest parts of an area |
| reptile | a vertebrate with scaly skin that lays eggs with tough, leathery shells |
| responding variable | the factor that changes as a result of changes to the manipulated variable in an experiment |
| rill | a tiny groove in soil made by flowing water |
| river | a large stream |
| runoff | water that flows over the ground surface rather than soaking into the ground |
| sand dune | a deposit of wind-blown sand |
| satellite images | pictures of the land surface based on computer data collected from satellites |
| scale | used to compare distance on a map or globe to distance on Earth's surface |
| scientific theory | a well-tested concept that explains a wide range of observations |
| sedimentary rock | the type of rock that is made of hardened sediment |
| sediment | Earth materials deposited by erosion |
| sod | a thick mass of grass roots and soil |
| soil conservation | the management of soil to prevent its destruction |
| soil horizon | a layer of soil that differs in color and texture from the layers above or below it |
| soil | the loose, weathered material on Earth's surface in which plants can grow |
| spit | a beach formed by longshore drift that projects like a finger out into the water |
| stalactite | a calcite deposit that hangs from the roof of a cave |
| stalagmite | a cone-shaped calcite deposit that builds up from the floor of a cave |
| stream | a channel through which water is continually flowing downhill |
| subsoil | the layer of soil beneath the topsoil that contains mostly clay and other minerals |
| symbols | on a map, pictures used by mapmakers to stand for features on Earth's surface |
| till | the sediments deposited directly by a glacier |
| topographic map | a map that shows the surface features of an area |
| topography | the shape of the land determined by elevation, relief, and landforms |
| topsoil | mixture of humus, clay, and other minerals that forms the crumbly, topmost layer of soil |
| trace fossils | a type of fossil that provides evidence of the activities of ancient organisms |
| tributary | a stream that flows into a larger stream |
| turbulence | a type of movement of water in which, rather than moving downstream, the water moves every which way |
| unconformity | a place where an old, eroded rock surface is in contact with a newer rock layer |
| valley glacier | a long, narrow glacier that forms when snow and ice build up in a mountain valley |
| variable | any factor that can change in an experiment |
| vertebrate | an animal with a backbone |
| weathering | the chemical and physical processes that break down rock at Earth's surface |
