Lava-. Molten rock that reaches the earth's surface through a volcano or fissure.The rock formed by the cooling and solidifying of molten rock.
Magma-The molten rock material under the earth's crust, from which igneous rock is formed by cooling.
Sedimentary rocks- rock formed from consolidated clay sediments.
Metamorphic Rocks- rock altered by pressure and heat.
Igneous Rock- rock formed by the solidification of molten magma.
Thursday, January 26, 2012
Bibliography
http://www.nysm.nysed.gov/nysgs/nygeology/mineralogy/adirondack-lowlands/index.html
http://schoolworkhelper.net/wp-content/uploads/2010/09/rock-cycle-diagram-im.jpg
http://www.ehow.com/facts_5514074_geological-history-catskill-mountains.html
http://www.adirondack-park.net/
http://gretchen.geo.rpi.edu/roecker/nys/adir_txt.html
http://schoolworkhelper.net/wp-content/uploads/2010/09/rock-cycle-diagram-im.jpg
http://www.ehow.com/facts_5514074_geological-history-catskill-mountains.html
http://www.adirondack-park.net/
http://gretchen.geo.rpi.edu/roecker/nys/adir_txt.html
Comparing Igneous, Sedimentary and Metamorphic Rocks.
Igneous rocks are formed when magma or lava cools and hardens. An igneous rock becomes a sedimentary rock through weathering and erosion of the igneous rock. The igneous rock, exposed to weathering processes at the surface, breaks into smaller pieces. Erosional processes transport these pieces to a place of deposition where they build up, layer on layer. Eventually the compaction caused by the weight of the sediments above reduces the amount of space and water between particles. In this process of rock formation known as lithification, cementing minerals are formed out of the slowly disappearing fluids, which are saturated with mineral components. Once cemented together, it is now considered sedimentary rock. Igneous rocks become metamorphic rocks once it has undergone metamorphism. Metamorphism is the change in form of a geological unit (like a rock) through metamorphic processes (must be in solid state). These processes include temperature and pressure changes as well as chemical changes. A sedimentary rock can be transformed into an igneous rock and then into a metamorphic. First Sedimentary rock can be changed into igneous rock by undergoing melting and then solidification. At a subduction zone layers of sedimentary rock will be assimilated into the mantle. Some areas may undergo enough heating to actually melt, especially if there is water or carbon dioxide trapped in the rock. If this rock later makes it to the surface and cools, it will become an igneous rock. Then a sedimentary rock can turn into a metamorphic rock by exposure to heat and/or pressure through depth of burial, directed pressure, or proximity to a magma source. Existing minerals can recrystallize, non-hydrous minerals can replace hydrous minerals, new minerals can be formed from the introduction of new ions from heated solutions, and minerals can become flattened and aligned in parallel layers.
Geology of the Appalachian Mountains
Adirondack Mountains
The rocks of the Adirondacks, almost without exception, are metamorphic. They have been subjected to high temperatures and pressures at depths of up to 30 km in the earth's crust. Most of the rocks in the Northwest Lowlands are metasedimentary or metavolcanic and have a complex history. The Adirondack mountains consist primarily of metamorphic rocks, mainly gneiss, surrounding a central core of intrusive igneous rocks, most notably anorthosite, in the high peaks region. The Adirondack Lowlands contains a diverse range of meta-igneous and meta-sedimentary rocks. The oldest lithologic unit is the Lower Marble formation consisting of calc-silicates, quartzites, gneisses, and tourmalinites. The Popple Hill gneiss composed of metamorphosed mudstones, slates, sandstones, and volcanogenic sequences overlies the lower marble.
Kimberlitic Rocks of New York State
Western New York State is noted for its flat-lying, sandstones, limestones, dolostones, siltstones, and shales. However, some very interesting igneous rocks can be found as dikes* intruding these Paleozoic sedimentary rocks in a narrow band that extends from the vicinity of Ithaca, through the Syracuse area, and beyond to Ogdensburg on the St. Lawrence River. These unusual rocks occur as narrow dikes that formed as molten rock from the upper portion of the earth's mantle pushed upwards into joints (vertical cracks) in the surrounding rock, then cooled, and solidified. The dikes range in size from an inch (2.5 cm.) or less, to 195 feet (60 m.) in width.Although igneous rocks characteristically contain radioisotopes that make it possible to determine their ages, several factors make it difficult to date these kimberlitic rocks. For example, different crystals in a sample formed at different times, and sometimes chunks of crystalline rock from the lower crust or upper mantle can become incorporated in the kimberlitic magma as it works its way upward. This results in an incorrect date if portions of it are sampled. Furthermore, post-crystallization alteration and weathering makes it difficult to extract suitable material for dating.
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