of Geology Terms

Terms not in this glossary might be found in the online geological dictionary at Iverson's WebRef

accretion-coalescence of smaller pieces into a larger mass.

albido-reflectivity of light and radiation from the surface.

alluvium-sediments deposited by a stream.

B.Y.A.-Billion Years Ago.

convection currents-movement caused by the rising of less dense, hotter materials and the concurrent sinking of more dense, cooler materials.

epicenter-land surface above the focus, or center of origin of an earthquake.

drift-glacial deposits.

esker-a snake-like ridge of roughly stratified sand and gravel formed by water flowing in or under a glacier.

insolation-radiant input from the sun.

interglacial period-warmer, humid to temperate periods occurring between episodes of ice cover.

isostatic rebound-"bouncing back" of the mantle (and the crust atop it) following the removal of weight.  The weight of thousands of feet of glacial ice would have depressed the plastic magma of the mantle.  When the ice weight was removed, the magma rebounds.

kame-a mound or short ridge of stratified sand and gravel deposited by water streaming under or trapped within glacial ice.

magma-semimolten rock.

magnitude-a measure of the energy released by an earthquake.

mechanical weathering-the process by which rock is broken down into smaller fragments as result of  physical forces; for example, water may seep into cracks in rocks,  freeze and expand, thus breaking up the rock.

microplate-small land areas of igneous rock; these are thought to have combined to form the larger tectonic plates and continents

Milankovitch cycles-Long period cycles in three orbital parameters that greatly influence Earth's climate, discovered by the Serbian mathematician Milutin Milankovitch.  This says that long term variations in Earth's orbital properties (axial tilt and eccentricity of orbit)  influence climate by changing the seasonal and latitudinal distribution of incoming solar radiation.

Modified Mercalli Intensity Scale-a system for measuring the intensity of an earthquake based on observation of its effects on an area, e.g., damage to structures.

M.Y.A.-Million Years Ago

orogeny-a period of mountain building

outwash-sand and gravel deposited by meltwaters streaming from the front of a glacier.

paleomagnetism-the study of the Earth's past based on the orientation of magnetic crystals frozen into igneous rocks.

physiographic province-Areas which have similar landscape, geology, and subsequently, biota.

Pre-Cambrian-a collective term for the time in Earth history before abundant fossils existed.  Comprising nearly 4 billion years, it includes the vast majority of Earth history, under the headings of the Pre-Archean (4.5-3.8 BYA), Archean (3.8-2.5 BYA), and Proterozoic (2.5-0.57 BYA) eons. 

Richter scale-A logarithmic scale measuring the amount of energy released during an earthquake on the basis of the amplitude of the highest peak recorded on a seismogram. Each unit represents a 10-fold increase in the amplitude recorded on the seismogram and a 30-fold increase in energy released by the earthquake.


striation-scratches left in bedrock materials which have been abraded by glacial ice usually carrying a grit of sand, gravel, and/or boulders.

subduction zone-when two tectonic plates collide, the denser plate will dive under the less dense one, being subducted.

terminus-the front edge of a glacier, which may be either advancing or retreating

till-unsorted, unlayered drift deposited directly by a glacier.

unconsolidated materials-loose sediments which have not been lithified (solidified) into rock.


Home | Introduction | Ice Age | Earthquakes | Historical Geology | Fossils | Sites of Geologic Interest | Glossary | References