GEOLOGY

 Rock - solid matter made from minerals or petrified organic materials.  Mineral - naturally occurring homogeneous inorganic solid having a definite chemical composition and a unique crystal structure, color and hardness

Igneous rocks - hot liquid cools and becomes rock. There are three types 1. Intrusive Igneous -- formed inside the earth from magma chambers Magma - Hot liquid found under the earth’s surface

Intrusive Textures  Porphyritic texture - large crystals imbedded in a smaller matrix Phenocryst - Conspicuously large crystal imbedded in a matrix of finer crystals

 Phaneritic texture- igneous rock texture - crystals are roughly the same size - large enough to be seen with the unaided eye EXAMPLES  Granite - phaneritic 25% quartz and 50% feldspar  Diorite - coarse grained intrusive - no visible quartz crystals  Gabbro - dark green/ black - pyroxene and plagioclase

2. Extrusive Igneous -- formed on the surface of the earth in a lava flow or lava shot from a volcano  Lava - molten rock that reaches the earth’s surface through a volcano or fissure Extrusive Textures Aphanatic - igneous rock texture in which the crystals are too small to be seen with the unaided eye

EXAMPLES of Aphanatic Textures  Rhyolite - volcanic equivalent of granite  Obsidian - dark colored glassy rock  Pumice - volcanic rock with a glassy texture  Andesite - medium grey fine grained rock  Basalt - dark green/ black - pyroxene and feldspar extrusive equivalent of gabbro

Crystallization - process where ions arrange themselves into orderly patterns as magma cools

3. Pyroclastic rocks- shot from a volcano (still igneous)  Tuff - frothy volcanic ash formed from huge sudden volcanic events  Volcanic breccia - volcanic rocks composed of particles larger than ash  Bombs - large solid rocks ejected by volcanoes

Sedimentary rocks - from when sediments from erosion are cemented together. There are two types 1. Clastic- made from broken pieces of other rocks  Made from Mud, silt, sand, gravel Examples: Shale- Mud and silt Sandstone- Sand Conglomerate- gravel

2. Chemical Sedimentary rocks - form from minerals dissolved in H2O  When temperature of water lowers ions come out of solution.  Have smooth textures -intergrown crystals EXAMPLES-  Rock salt - Halite  Limestone (not all)  Rock Gypsum

 Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks.  The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change underground.  As a result, most of the thousands of rare minerals known to science occur in metamorphic rocks.  The presence of mineral layers, called foliation, is important to observe when identifying a metamorphic rock.

 Metamorphic rocks form deep in the earth where high temperature, great pressure, and chemical reactions cause one type of rock to change into another type of rock.  This happens kilometers beneath the earth's surface and at temperatures of 100 degrees Celsius to 800 degrees Celsius.  If you squeeze and heat a rock for a few million years, it can turn into a new kind of rock

 Classified by texture and composition  May have alternate bands of light and dark minerals  May be composed of only one mineral, ex. marble & quartzite  May have layers of visible crystals  Usually made of mineral crystals of different sizes  Rarely has pores or openings  May have bent or curved foliation

 Some examples of how metamorphic rocks were changed:

 Inner Core Nickel and Iron Solid -- diameter is 1480 km  Outer Core Nickel and Iron Liquid km thick

Lower Mantle Solid km thick Upper mantle (Athenosphere) Plasticlike part is 600 km Rigid top part is 75 km

 Crust Continental -- Si rich Oceanic -- Fe and Mg rich

 When two tectonic plates collide one may be pushed down into the mantle. It heats and melts  Magma that is made will have different chemical composition depending on where it comes from.

 Magmas from Continental Crust - rich in silicon and aluminum  Magmas from oceanic crust - rich in iron and magnesium  Composition determines which rocks will be made when magma cools

 N.L. Bowen - showed that cooling magmas produce minerals in a predictable order  Two sides - Iron (Fe) rich side and a calcium / sodium (Ca / Na) rich side.

 Olivine - First Fe rich mineral to form - in tetrahedra shape - easily weathered on the surface  Pyroxenes - Tetrahedra link in long chains - also weather easily

 Amphiboles - double strands made from linking pyroxenes  Micas - amphibole chains make sheets  Feldspar - from the Ca/Na side like olivine but Al is inside the tetrahedra vs. Si

 Feldspars - as temp cools Ca and Na replace Al inside the tetrahedron  Quartz - very low temperatures - little left in magma except Si and O -three dimensional networks