to remove a cylinder of material, much like a hole saw.Drumlin - an elongated whale-shaped hill formed by glacial action.Dunite - Ultrabasic plutonic rock in which mafic material is almost entirely olivine with accessory chromite almost always present. Feldspar mainly plagioclase. See Peridotite.Duricrust - General term for hard crust on surface of or layer in upper horizons of a soil in semi-arid climate formed by accumulation of solid minerals deposited by water moving upwards by capillary action and evaporating in the dry season. Cf HardpanE[edit]Eclogite - Generally coarse to medium grained, green (reddish when weathered) pyroxene in which are set red garnets. Pistachio green when fresh, but mottled with red when weathered.Eemian transgression - Late Pleistocene 120 Ka. up to 8m above presentEon - the largest unit of geologic time.Epicenter - point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or other underground explosion originates.Epidiorite - altered gabbroic and doleritic rocks in which the original pyroxene has been replaced by fibrous amphibole. The rock may be regarded as a first step in the conversion by dynamothermal metamorphism of a basic igneous rock into a green schist.Epirogenetic - simultaneous rising and falling movements of continents, maintaining isostasyEpoch - each period of the standard geologic time scale is divided into epochs (e.g., Pleistocene Epoch of the Quaternary Period).Erosion - displacement of solids (sediment, soil, rock and other particles) usually by the agents of currents such as, wind, water, or ice by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion).Erratic - piece of rock that deviates from the size and type of rock native to the area in which it rests; stones ranging in size from pebbles to large boulders which were transported by ice, which on melting left them stranded far from their original source; the name "erratic" is based on the errant location of these boulders.Escarpment - transition zone between different physiogeographic provinces that involves an elevation differential, characterized by a cliff or steep slope.Esker - long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America. Eskers are frequently several miles in length and, because of their peculiar uniform shape, somewhat resemble railroad embankments.Estuary - semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.Eugeosyncline - A geosyncline in which volcanism is associated with clastic sedimentation: The volcanic part of an orthosyncline located away from the craton.Euhedral - rock minerals which are bounded by the crystal faces peculiar to the species; ideomorphic.Eustatic movements - Changes of sea level, constant over wide areas, due to alterations in the volume of the oceans resulting from formation or melting of ice caps.Evaporite - water-soluble, mineral sediments that result from the evaporation of bodies of surface water.Exfoliation - the stripping of concentric rock slabs from the outer surface of a rock mass.Extension - strain involving an increase in length. Extension can cause