Geology and Oceanography
rock aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic. Igneous Rocks Igneous rock originates from the cooling and solidification of molten matter from the earth's interior. If the rock is formed on the earth's surface (i.e., from the solidification of lava), it is called extrusive rock; igneous rock that has cooled and solidified slowly beneath the earth's surface is intrusive rock. Among the forms commonly taken by intrusive rocks are batholiths , which are enormous, irregular masses cutting or displacing older rocks; stocks, irregular and smaller than batholiths; necks, or plugs, columnar in form and probably the result of the hardening of magma in the necks of extinct volcanoes; dikes, more or less vertical, filling fissures in previously existing rock; sills, more or less horizontal, forced between layers of previously existing rock; and laccoliths, modified domelike sills that arch under the overlying rock. Igneous rocks are commonly divided into classes by texture. Some rocks are markedly granular (e.g., granite , syenite, diorite, gabbro, peridotite, and pyroxenite), while others (e.g., basalt , trachite, dacite, and andesite) are composed of grains visible only under a microscope. Both fine-grained and coarse-grained igneous rocks frequently...
sedimentary rock Type of rock formed by deposition of sediment derived from pre-existing rocks, which may have been sedimentary, igneous or metamorphic. Most sediment accumulates on the bed of the sea, having been dumped there by rivers, or having accumulated as dead sea creatures fall to the seafloor. This accumulated sediment is consolidated and compressed. Earth movements uplift the sediments, and they may be tilted, folded or faulted. The resulting rocks are sedimentary, and their type depends on their composition. Sedimentaries consisting of land sediment are clastic rocks, and are gravels, sands, silts or clays, according to the size of the particles. Other types of sedimentary rock include: limestone, which consists of fragments of dead sea creatures; coal, which is accumulated vegetation; coralline, which contains large quantities of coral; and chalk, which is a pure form of limestone, with very little land sediment. See also fault; fold
Are you looking to learn about the earth and the oceans that cover it? You’ve come to the right place. Our geology and oceanography content includes information as diverse as discussions about artesian wells and breakwaters, to broad descriptions of the Cambrian period and geo chemistry. This content also covers geysers, hardpan, each known ice age, and a host of other interesting and dynamic cont ... Read more
ent. Beyond covering the facts of these areas, we also cover some of the people who have studied the oceans as well as geology. These include doctors, scientists, oceanographers, and chemists whose studies led to new and amazing discoveries.