Chapter 3. ROCKS NJCCCS: 5.4 C – Properties of Earth Materials. What is a Rock?. It is a mixture of minerals, mineraloids , glass, or organic matter ex . Granite = mica + quartz + feldspar + hornblende + other minerals. The Rock Cycle. Rock Type Basics.
ROCKS NJCCCS: 5.4 C – Properties of Earth Materials
What is a Rock? It is a mixture of minerals, mineraloids, glass, or organic matter ex. Granite = mica + quartz + feldspar + hornblende + other minerals
The Rock Cycle
Rock Type Basics Igneous Rocks – form from cooling magma or lava Metamorphic Rocks – form from extreme heat and pressure Sedimentary Rocks – form from the compaction and cementation of sediment (rock fragments)
Weathering (breaking rocks into smaller pieces) Mechanical Weathering – does change chemical composition Chemical Weathering – changes the chemical composition
Erosion Main Agents of erosion 1. Wind 2. Water 3. Glaciers 4. Gravity 5. Animals
Heat and Pressure Heat – radioactive decay, extreme pressure Pressure – thousands of miles of rock pulled together by gravity
Melting Caused by heat due to radioactive decay and pressure
Igneous Rocks Igneous Rocks - cooled molten material form the inside the Earth(magma) or out of a volcano (lava) - the most common rock on Earth
Igneous Rocks B. The Earth’s crust generates great temps (1400), pressures, and radioactive thermal energy C. Rocks and Minerals melt to form magma, minerals have different densities and melting pts
Igneous Rocks D. Magma is less dense than the crust above and forces an escape through volcanoes as lava E. Sometimes magma forces upwards but cools before reaching the surface
Classification of Igneous Rocks (1) Intrusive Igneous Rocks - those rocks that were formed from cooling magma below the Earth’s surface Cool very slowly Have large crystals called mineral grains Extrusive Igneous Rocks - Rocks that formed from cooling lava on the surface of the Earth -Cool very quickly - Have very fine grained texture
IGNEOUS ROCKS – cooled magma or lava Intrusive igneous rocks have large mineral grains!!!!! Extrusive igneous rocks have virtually no mineral grains.
Classification of Igneous Rocks (2) 1. Basaltic – dense, heavy, dark colored rock, rich in magnesium and iron, most common 2. Granitic – light color, less dense, rich in silicon and oxygen 3. Andesitic – mineral compositions in between the two, common among Pacific Volcanoes
ANDESITE BASALT GRANITE
Intrusive Igneous Features Magma Chamber is a large underground pool of molten rock found beneath the surface of the Earth.
Intrusive Igneous Features Sill is an intrusion of magma that solidifies into a horizontal layer of igneous rock
Intrusive Igneous Features Dike is a magma that cuts across rock layers (vertical)
Intrusive Igneous Features Batholith is a magma chamber that cools before reaching the surface to form a volcano
Intrusive Igneous Features Laccolith is a small magma chamber at shallow depth (roughly lens shaped)
Extrusive Igneous Features Volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface 3 types: Shield Composite Cinder
Extrusive Igneous Features Lava Flow – different types of lava depending on the composition and temperature
Extrusive Igneous Features Ash and Dust Particles
Extrusive Igneous Features Pyroclastic Flow is a fast-moving current of extremely hot gas ( 1,830 °F) and rock which travel away from a volcano at speeds generally as great as 450 mph.
Sedimentary Rocks 3 Types of Sedimentary Rocks 1) Clastic – made from rock fragments 2) Chemical – evaporation or precipitation from solution 3) Organic – contains fossils
Classification of Sedimentary Rocks 1) Clastic Made from sediments
Organic Sedimentary Rock Coal – formed from the Remains of plants at the Bottom of a body of water Limestone – formed from the mixed skeletal remains of marine organisms
Chemical Sedimentary Rock Gypsum – easily dissolves in water… gypsum rock forms when the water evaporates and crystallizes Halite – (salt) – easily dissolves in water…halite forms when the water evaporates and crystallizes
Metamorphic Rocks Metamorphic Rocks - rocks that have changed due to increases in temperature and pressure - igneous, sedimentary, metamorphic rocks can metamorph B. Ex. Basalt Schist Gneiss Shale Slate Phyllite Gneiss Granite Gneiss
Metamorphic Rocks Occurs in 2 general ways: 1) Contact Metamorphism 2) Regional Metamorphism
Contact Metamorphism As magma pushes through rock layers beneath the Earth…nearby rock change slightly in composition and structure
Regional Metamorphism As the Earth’s plates move, the same extreme pressures that build mountains also cause rocks to deform and change in composition
WHAT HAPPENS? Heat - (2 sources- magma and depth) Minerals within the rock melt and re-crystalize thus changing the composition of the rock
WHAT HAPPENS? Pressure – causes space between minerals to close – compacted often causing minerals to recrystalize
2 classifications Foliated – banded (layers) of minerals at 90 degree angles to the pressure that caused the metamorphism Non-Foliated – no bands or layers (usually composed of only one type of mineral)
Metamorphic Rocks – HEAT AND PRESSURE FOLIATED = bands of mineral grains NON-FOLIATED = no bands of mineral grains
Rock Classification Igneous Metamorphic Sedimentary Intrusive Foliated Clastic Extrusive Non-Foliated Chemical Organic Basaltic Andesitic Granitic
NJCCCS: 5.4B History of the Earth 5.4.12.B.1, 2, 3
Fossils Fossil - any naturally preserved evidence of past life
Understanding Decomposition When an organism dies specialist organisms called decomposers and detritivores begin consuming its remains. Decomposers are usually bacteria and fungi (think sour milk and moldy bread) Detritivores are animals like vultures, hyenas, insect larvae, and a host of others (think maggots in a garbage can) Most often only the hard tissue of the organism is left behind… bones and teeth, shells, exoskeletons, etc. See Video clip – Blue Planet
Fossils Are Rare Fossils only form under very special environmental conditions!!!!!!! Usually found in sedimentary rocks…why? Exceptions: Volcanic ash
3 ways in which fossils form 1) Mineral Replacement 2) Mostly Unchanged 3) Trace
Mineral Replacement Underground water removes original material 1 atom at a time and replaces it with minerals. An exact copy is created out of the minerals calcite, pyrite, or silica. *Most Common way in which fossils form 3 basic types Petrification, Molds, Casts
1) Petrification the organism gets totally replaced with minerals
2) Molds dead creature is covered with sediments and decays away. The remaining cavity in the shape of the original creature is the fossil = impression
3) Cast Minerals from ground water seep into the mold, precipitate out of solution, and a stone shape is the fossil
Mostly Unchanged Actual original parts of an organism are left behind by several methods. 1) Simple Burial 2) Frozen 3) Amber 4) Mummification 5) Acidic Peat Bogs 6) Tar SPECIAL ENVIRONMENTAL CONDITIONS EXIST THAT PREVENT DECOMPOSITION!!!!
1) Simple Burial bones and teeth most often remain…share similar properties to minerals (calcium carbonate)
2) Frozen soft parts of mammoths have been found in frozen arctic tundra Why do we put food in a freezer? Slows down decomposition!!
3) Amber resin or ancient tree sap captured creatures (insects, frogs, etc.)
4) Mummification creatures desiccate (dry out) and soft parts remain – salt and or lye prevent decomposition
5) Acidic Peat Bogs creatures have been preserved in some wetlands that have environmental conditions that prevent decomposition (lack of oxygen, extreme pH)
6) Tar ancient oil seeping from underground trapped creatures. La Brea Tar Pits in California hold bones of mammoths, sabertooth tigers, camels, and more. Tar prevented decomposition.
Trace Fossil Evidence Evidence of past life not including plant or animal remains