Chapter 02

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Chapter 02

  1. 1. Minerals Rocks igneous sedimentary metamorphic Minerals form rocks Three rock types have different properties because they form in unique ways Rock cycle interrelates all rocks Environmental Geology jbartlett@national.edu
  2. 2.       Naturally occurring Inorganic Solid element or compound Definite chemical composition Regular internal crystal structure Identified by recognizing different physical properties Figure 2.4B Figure 2.4C
  3. 3.   The two fundamental characteristics of a mineral are its chemical composition and its crystal structure Analyze the mineral composition • Technology based  Measure crystal structure and symmetry • Technology based  Observe and measure physical and special properties • Easy for humans to see and recognize  Color  Hardness  Cleavage  Luster  Density  Form
  4. 4. Table 2.1
  5. 5.     A solid aggregate of one or more minerals, or mineral materials Consists of many mineral grains or crystals forming a solid mass Each rock contains a record of its own history Three broad categories • Igneous: • Sedimentary: • Metamorphic:  cooled from melted magma deposited from physical or chemical parts altered from previous rocks Three rock types each show a particular texture from the process of formation • Igneous: • Sedimentary: • Metamorphic: Crystalline and interlocking granular and layered warped, banded or squeezed
  6. 6. Igneous Rocks formed by the solidification and crystallization of a cooling magma      Rocks formed from hot, molten rock material [magma] Usually composed of silicate minerals + some dissolved gases + water Plutonic rocks form if magma cools inside earth’s crust (does not flow onto surface); coarse crystals will grow Volcanic rocks form if magma flows onto surface as lava; glass often forms Coarse, visible crystals indicate time spent cooling = depth underground St Cloud Granite St Cloud, MN 1.7 + billion years old
  7. 7. Igneous Rocks Felsic Intermediate low iron light toned Mafic high iron dark toned Volcanic: Surface, fine grained Rhyolite Andesite Basalt Plutonic: Deep, coarse grained Granite Diorite Gabbro
  8. 8. • • • • • Sediments are accumulations of mineral or rock particles produced by weathering of pre-existing rocks and minerals Sediments are eroded, transported, and deposited and buried in many sedimentary environments Gravity and transport play a role in the formation of all sedimentary rocks Layering is a very common feature of sedimentary rocks and is used to identify the origins of sedimentary rocks Sedimentary rocks are formed at or near the earth’s surface and at temperatures close to ordinary surface temperatures. St Peter Sandstone St Paul, MN 455 million years old
  9. 9.       “Changed form” rock Rock formed from pre-existing rock or minerals Heat, pressure, and chemically active fluids cause changes in rock Heat increases as a rock is buried or is close to magma – not quite melting but can have big effect such as recrystallization Pressure increases with burial or collision between moving continents and can cause deformation, recrystallization Fluids become heated and circulate with burial or with location near a magma chamber Morton Gneiss Central MN 2.5 + billion years old
  10. 10.     Any kind of preexisting rock (another rock) can be metamorphosed Foliation: when a rock is subjected to directed stress, its minerals form elongated/platy crystals and line up parallel to each other Metamorphic rocks without foliation do not show directed stress • Marble is metamorphosed limestone • Quartzite is metamorphosed quartz-rich sandstone Metamorphic rocks with foliation show directed stress or pressure • Slate – low grade foliated metamorphic rock • Schist and Gneiss (nice) – high grade metamorphic rocks
  11. 11.    Shows the interrelationships among the three rock types Rocks of any type can be transformed into rocks of another type or into another distinct rock of the same general type through the geologic processes Rocks are continually being changed by geological processes

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