Datum plane: An artificially established, well surveyed horizontal plane against which elevations, depths, tides, etc. are measured (for example mean sea-level).

Daughter element: Also "daughter product". An element that occurs in a rock as end product of the radioactive decay of another element.

Debris avalanche: A fast downhill mass movement of soil and rock.

Declination: At any place on Earth, the angle between the magnetic and rotational poles.

Deflation: The removal of clay and dust from dry soil by strong winds.

Delta: A body of sediment deposited in an ocean or lake at the mouth of a stream.

Delta kame: A deposit having the form of a steep, flat topped hill, left at the front of a retreating continental glacier.

Dendritic drainage: A stream system that branches irregularly and resembles a branching tree in plan.

Density: The mass per unit volume of a substance, commonly expressed in grams/ cubic centimeter.

Density current: A subaqueous current that flows on the bottom of a sea or lake because entering water is denser due to temperature or suspended sediments.

Deposition: A general term for the accumulation of sediments by either physical or chemical sedimentation.

Desert pavement: A residual deposit produced by continued deflation, which removes the fine grains of a soil and leaves a surface covered with closely packed cobbles.

Detrital sediment: A sediment deposited by a physical process.

Diagenesis: The physical and chemical changes undergone by a sediment during lithification and compaction, excluding erosion and metamorphism.

Diatom: A one celled plant that has a siliceous framework and grows in oceans and lakes.

Diatomite: A siliceous chert-like sediment formed from the hard parts of diatoms.

Diatom ooze: A fine muddy sediment consisting of the hard parts of diatoms.

Diatreme: A volcanic vent filled with breccia by the explosive escape of gases.

DICTIONARY:It is a reference book.You can be found: meaning of words, translation, synonyms, tenses, grammatical information, pronunciation, abbreviations, examples, images, derivations and grossed reference.

A book giving information on particular subjects or on a particular class of words, names, or facts, usually arranged alphabetically: a biographical dictionary; a dictionary of mathematics.

differential: is a device, usually but not necessarily employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways. In one way, it receives one input and provides two outputs; this is found in most automobiles. In the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs.

Dip: The angle by which a stratum or other planar feature deviates from the horizontal. The angle is measured in a plane perpendicular to the strike.

Divide: A ridge of high ground separating two drainage basins emptied by different streams.

Dome: In structural geology, a round or elliptical upwarp of strata resembling a short anticline.

Drainage basin: A region of land surrounded by divides and crossed by streams that eventually converge to one river or lake.

Drift (glacial): A collective term for all the rock, sand, and clay that is transported and deposited by a glacier either as till or as outwash.

Drumlin: A smooth, streamlined hill composed of till.

Dry wash: An intermittent streambed in an arroyo or canyon that carries water only briefly after a rain.

Dune: An elongated mound of sand formed by wind or water.