Ice Age Floods
Back-arc SpreadingThe region of crustal spreading between a volcanic archipelago and the continental interior.
BarsEddy or Shoulder BarsFormed downstream from promontories or recesses.
Pendant BarsExtended downstream behind the protection of a rock island or other obstruction.
Expansion BarsFormed where the water spreads out after passing through a narrow point and deposits material.
BasaltA dark-colored fine-grained extruded volcanic rock, rich in iron and magnesium, that is chiefly composed of plagioclase and pyroxene.
BasinA large circular or elliptical depressed area in a landscape.
Braided RiverA stream system so overloaded with sediment that there are many dividing and rejoining channels.
ColonnadeThe lower portion of a lava flow with well-formed parallel shrinkage columns, usually vertical.
Columnar JointingLong joints, usually vertical, in volcanic rock that splits into columns as the rock cools and contracts.
Continental GlacierA thick ice sheet covering a large part of a continent.
CouleeA dry trench-like intermittent streambed or wash.
DeltaA low, flat tract of land at the mouth of a river, composed of stream-deposited sediment, and triangular in shape from an aerial view.
EntablatureThe upper portion of a lava flow that displays irregular thin shrinkage columns.
ErraticA large rock that is not of local origin and has been moved to its location by glacial ice.
FaultA break in the earths crust along which movement has taken place. Frequently occurs as a zone of numerous smaller faults.
Fault TraceIntersections of faults on the ground surface (horizon); also called fault line.
FaunaThe entire animal population living in a given area, environment, or time span.
Flood BasaltA plateau basalt. Successive flows of high temperature fluid basalt from fissure eruptions merge to form a continuous flat plateau.
FloraThe entire plant population living in a given area, environment or time.
FloodplainThe flat area where a stream or river may overflow.
GlacierA mass of ice and snow that moves downhill because of gravity.
Graded BeddingRapid sedimentation leaving a distinctive texture of coarse grains followed by fine grains in a single layer. See Rhythmites.
Hanging ValleysSmaller glacial valleys feeding into a deeper main glacier trough.
JökulhlaupAn ice dam failure or glacial outburst
Kolk LakeA hole eroded by rushing water at the base of a broken dike; a deep pool, eddy or scour area which has filled with water.
LithosphereThe outer 60 miles of the earth between the crust and mantle where the rocks are harder and more brittle.
LodeDeposits in which ores have been emplaced into rock formations where they occur in veins.
LoessNon-stratified silt, clay, and dust, originating as glacial sediment, but re-deposited by wind. Wind-blown silt.
MagmaA silica-rich molten fluid that appears on the surface as lava and that cools underground as a pluton.
Magma Chamber A magma reservoir in the shallow part of the lithosphere.
Plunge PoolA spot at the base of a waterfall where the descending force of the water strikes the bottom and carves out a basin. A deserted plunge pool is one whose waterfall has migrated upstream.
PotholeA bowl-shaped depression in a rock surface that has been carved by the whirling action of stones in a stream bed.
RhythmitesLayers consisting of gravel or sand at the base, followed by silt on top, representing separate flooding events.
RiftA distinct, roughly linear trough or depression on the earths crust that reflects a pulling apart of the crust due to tension.
Ripple MarksDeposits left by currents flowing over the bottom that shape the sediments into smooth, parallel, ridge rows resulting in washboard-like ripples that are regularly patterned.
SandRock and mineral fragments ranging in size between 1/16 and 2 millimeters in diameter.
ScablandAn irregular land surface of basalt that has been scoured of its soil cover by floods.
SpillwaysLow divides that have been overtopped by floodwaters.
StrandBeach and very shallow coastal area dominated by shoreline processes, particularly wave processes.
Subduction TrenchA distinct linear groove on the earths crust marking the boundary between two colliding tectonic plates in which one plate slips beneath another.
Submarine CanyonA steep V-shaped trench along or across a continental shelf or deep ocean floor.
TillLoose sediment deposited by glaciers.
WatershedThe total area drained by a stream system.