Thursday, January 26, 2012

5 Definitions

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.

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

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




  The Appalachian Basin is one of the most important coal producing regions in the US and one of the biggest in the world.     The range is mostly located in the United States but extends into southeastern Canada, forming a zone from 100 to 300 mi (160 to 480 km) wide, running from the island of Newfoundland 1,500 mi (2,400 km) south-westward to Central Alabama in the United States. Appalachian Basin bituminous coal has been mined throughout the last three centuries. Currently, the coal primarily is used within the eastern U.S. for electrical power generation, but some of it is suitable for metallurgical uses. Economically important coal beds were deposited primarily during Pennsylvanian time in a southeastward-thickening foreland basin. Coal and associated rocks form a clastic wedge that thickens from north to south, from Pennsylvania into southeast West Virginia and southwestern Virginia. The geology of the Appalachians dates back to more than 480 million years ago.  A look at rocks exposed in today's Appalachian mountains reveals elongated belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor, which provides strong evidence that these rocks were deformed during plate collision
                                                                                                                                 

  

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 historyThe 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.