Earth Science Exam 2 Outline I Minerals A Properties of Minerals 1 Crystal Formxternal appearance of a mineral as determined by its internal arrangement of atoms Orderly arrangement of atoms 2 Colorin minerals is caused by the absorption or lack of absorption of various wavelengths of light When pure white light that is containing all wavelengths of visible light enters a crystal some of the wavelengths are absorbed while other wavelengths are reflected 3 Streak s closely related to color but is a different property because the color of the mineral may be different than the color of the streak Streak is actually the color of the powder of a mineral 4 Lusters the appearance or quality of light reflected from the surface of a mineral It has nothing to do with color or shape The terms used are generally not scientific but are meant to be descriptive 5 Cleavages a smooth break producing what appears to be a flat crystal face Cleavage occurs in minerals that have specific planes of weakness 6 Hardness 1 Talc 2 Gypsum 3 Calcite 4 fluorite 5 apatite 6 Orthoclase 7 quartz 8 Topaz 9 Corundum 10 Diamond 2 5 Fingernail 3 5 Penny or Copper 5 5 Glass 7 Specific Gravity is a measure of the density of a mineral Specific gravity or SG as already stated compares the density of a mineral to the density of water If a mineral has a SG of 2 then it is twice as dense as water B Groups of Minerals and How they are Classified 1 Silicate Minerals contain the elements Si and O2 most abundant minerals in earths crust 3 4 of crust are Si and O2 classified by their silicate structure and chemical composition 2 Non Silicate Minerals Only about 8 of crust are non silicate Classified by their chemical composition Important economically II Rocks A Introduction to Rocks 1 Definitions a solid mass of mineral or mineral like matter that occurs naturally 2 Rock Cycle B Types of Rocks 1 Igneous How they are formed Intrusive plutonic rocks cool slowly far beneath the Earth s surface Extrusive volcanic rocks cool quickly on or near the Earth s surface b Texture and Chemical Composition ranitic felsic composed mostly of the light silicate minerals quartz and potassium feldspar which are generally white to pink in color 2 Andesitic intermediate composed mostly of the minerals amphibole and sodium rich plagioclase feldspar with some quartz and pyroxene possible Intermediate igneous rocks are usually light to dark gray in color 3 Basaltic mafic composed mostly of the dark silicate minerals pyroxene calcium rich plagioclase feldspar and olivine Mafic rocks are usually black to dark green in color c Bowens Reaction Series 2 Sedimentary rock formed by the compaction and cementation of sediment derived from mechanical and chemical weathering a How they are formed rocks are formed from the weathering of other rocks igneous metamorphic or sedimentary rocks and the cementation and compaction or the precipitation and re crystallization of these broken pieces of rock 1 Weathering 1 1 Mechanical weathering when rocks are fragmented without changing its mineral composition as for example with waves or wind 1 1 1 abrasion water wind and ice are capable of moving rocks As rocks pebbles sand and larger rocks grind and scrape against each other rock material is worn away 1 1 2 frost wedging occurs when temperature freezes at night and rises during the day Water expands when frozen which forces rocks open 1 1 3 biological weathering Roots of plants grow into cracks and force cracks open 1 1 4 unloadingRocks that are buried beneath the surface may be lifted to the surface as rocks above are weathered away Removal of overlying rock reduces pressure along the surface The lower layers of rock fold upward and break Chemical weatheringwhen a rock is broken down by chemical reactions that change its mineral 1 2 composition and physical and chemical properties b Types of Sedimentary Rocks 1 Detrital Sedimentary 1 1 Compaction is the squeezing together of layers of sediment due to the great weight of overlying layers of rock When the layers are reduced in thickness the pore spaces around the sediments are also reduced which leads to a tighter packing of the layers 1 2 Cementation is the changing of sediment into rock by filling spaces around the sediments with chemical precipitates of minerals binding the sediments and forming solid rock Calcite and silica are common minerals that cement the sediments together 2 Chemical Sedimentary 2 1 Recrystallization or Precipitation 3 Metamorphic even from other metamorphic rocks a How they are formed Rocks that are produced from pre exsisting igneous sedimentary or Metamorphism takes place where rock is subjected to heat pressure and chemically active fluids Low grade metamorphism not a lot of change shale to slate High Grade great change parent rock cannot be determined 1 Heat most important energy to drive chemical reactions that result in recrystallization or formation of new minerals in rock a Contact or thermal metamorphism when magma intrudes into rock heats up rock can cause b Transportation to greater depths within earths crust 2 Pressure a Confining pressure reduces volume of rock makes it more dense b Differential stress makes rock thinner and longer b Types of Metamorphic Rocks 1 Foliated 2 Non Foliated III Running Water Streams A Introduction and Water Cycle Streams are any body of water that is flowing downhill in a well defined channel B Are an essential component in the hydrologic cycle Carry most of the water that goes into the oceans Transport billions of tons of sediment small amounts of dissolved salts Are an effective agent of erosion Important for Energy production transportation irrigation B General terms 1 Erosion is the process by which soil and rock are removed from the Earth s surface by exogenetic processes such as wind or water flow and then transported and deposited in other locations 2 Gradientis the slope of the stream channel or number of feet dropped per mile as measured between two points along the path of the stream common feature of river deltas 3 Distributaries is a stream that branches off and flows away from a main stream channel They are a 4 Tributaries is a stream or river that flows into a main stem or parent river or a lake C Factors affecting Stream Velocity 1 Gradient is the slope of the stream channel or number of feet dropped per mile as measured between two points along the path of the stream 2 Shape and Roughness of Stream channel a deep narrow channel or a