The theory that the Earth's outer shell is made up of about a dozen lithospheric plates that move about and interact at their boundaries. Permanent deformation (change in size or shape) of soft, but solid rock by folding or flowing without fracturing.Ī slab of rigid lithosphere ( crust and uppermost mantle) that moves over the asthenosphere. Generally tiny animals or plants that live floating in water. Feldspar crystals are stubby prisms, generally white to gray and a glassy luster. Plagioclase feldspars are silicates that contain considerable sodium and calcium. Differs from less recrystallized slate by its sheen, which is produced by barely visible flakes of muscovite ( mica).Ī member of the feldspar mineral family. Phyllites are usually black or dark gray the foliation is commonly crinkled or wavy. Like all micas, phlogopite forms flat, plate-like crystals that cleave into smooth flakes.Ī very fine-grained, foliated metamorphic rock, generally derived from shale or fine-grained sandstone. Phlogopite is a yellowish-brown to coppery-colored mica. See ' porphyritic'.Ī magnesium-rich member of the mica mineral family. The portion of Earth history with rocks containing abundant fossils.Ī term used to describe large crystals embedded in a mass of finer crystals (groundmass) in an igneous rock. The eon beginning about 570 million years ago and continuing to the present. May be a petrologist, a stone mason, a rock climber.Īn igneous rock texture in which the mineral grains are large enough to be seen with the unaided eye and are of approximately equal size. Permeable bedrock makes a good aquifer, a rock layer that yields water to wells. The ability of a rock or other material to allow water to flow through its interconnected spaces. Mudstone, shale, siltstone, and claystone are all pelitic.Ī stream that runs continuously throughout the year. Forms sills and dikes.Ī fine-grained sedimentary rock consisting mostly of clay and/or silt. Usually forms from molten rock rich in water or other volatiles that facilitate the growth of large crystals. Pebbles are the smallest type of gravel.Ī very coarse-grained igneous rock, commonly with a granitic composition. Loose particles of rock or mineral ( sediment) that range in size from 2 - 64 millimeters in diameter. The preexisting rock from which a metamorphic rock forms.Ī tectonically inactive continental margin characterized by a lack of earthquakes and volcanic activity.Ī bare rock surface that provides a protective rock cover over the material beneath it.Ī sloping bedrock surface at the base of a mountain, formed when erosion removes much of the mountain's mass. The supercontinent which formed at the end of the Paleozoic Era and began breaking up about 200 million years ago to form today's continents.Ī radioactive isotope that changes to a different, daughter isotope when its nucleus decays. Includes the time from about 570-245 million years ago. The study of ancient seismic ( earthquake) events. The orientation of iron-bearing magnetic minerals record the location of the Earth's magnetic poles and the latitude of the rock at the time of cooling. As the rocks cool, iron-bearing minerals are 'frozen' into position. Natural magnetism is acquired by some rocks, especially igneous rocks that are rich in iron, as they solidify. The study of how global climate has changed through time. The science that studies the past distribution of plants and animals.
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