| A | B |
|---|
| geologic time scale | a chart that organizes events in Earth's history |
| fossils | the imprints or remains of an organism that were once alive |
| absolute age | the actual age of a rock or fossil |
| radioactive dating | means of finding the age of a material by comparing the amount of a radioactive element in a rock or fossil with it's decay product |
| relative age | describes the age of an object compared to something else |
| law of superposition | states that in undisturbed rock layers, older layers lie beneath younger layers |
| unconformity | a missing layer in rock, a gap in the rock record |
| extinct | an organism that is no longer found on Earth |
| index fossil | helpful in determining the age of rocks, the fossil of an organism that only existed for a relatively short period of time |
| mass extinction | more than 50% of all living things die out at once |
| evolution | change over time |
| natural selection | theory that explains how organisms respond to changes in their environments |
| adaptation | a trait that improves an organisms chance for survival |
| continental drift | continents are slowly moving around the surface of the earth |
| plate tectonics | theory that the lithosphere is broken into plates that move or change position over time |
| convection currents | movement of the magma in the mantel that pushes the tectonic plates around the earth |
| convergent | boundary where two plates push together |
| divergent | boundary where two plates are pulling apart |
| transform | boundary where two plates are sliding past each other |
| subduction | where an oceanic plate sinks beneath another oceanic or continental plate |
| volcano | a landform formed from magma rising to Earth's surface |
| earthquake | occur when energy is released from two plates sliding past each other |
| fault | a break or crack in Earth's surface |
| hot spot | a volcanic area in the middle of a plate |
| mechanical weathering | breaks rocks apart without changing their physical compostion |
| chemical weathering | changes the chemical composition of rocks |
| electromagnetic spectrum | all of the electromagnetic waves |
| relfectance curve | graph that shows how matter reflects radiation |
| spectral analysis | study of the reflectance of radiation from Earth using computers |
| topographic maps | show the location and elevation of a region using contour lines and colors |
| contour line | a line on a topographic map that connects all areas with the same elevation |
| ground truthing | visiting an area to verify accuracy of a map from a photograph |
| remote sensing | collecting information about an area without visiting an area |
| urban sprawl | spreading out of a city's feature |
