Rock Cycle
A model that describes the formation, breakdown, and reformation of a rock. Sedimentary Rock •Formed when sediments accumulate and compact and cement together. •Often deposited in layers and contain sand, pebbles, and frequently fossils. Ex. sandstone, limestone Physical properties of Sedimentary Rocks •Sand, pebble, and even boulder size particles •Some may contain fossils By what process are sedimentary rocks broken down? Weathering •By weather (rain, ice, wind), chemical changes, and living things (plant). •Creates lose material called sediments. By what process are sediments moved? Erosion •Wind •Water •Gravity •Ice They are deposited in layers - Deposition What are the processes that form sedimentary rock? Compaction Sediments are deeply buried, placing them under pressure because of the weight of overlying layers. Cementation •New minerals stick the sediment together just like cement. •This holds the grains together tightly. Metamorphic Rock •Formed by heat and pressure while buried deep below Earth’s surface. •Have a layered or banded (ribbon like) appearance or may have crystals. Ex. Gneiss, Marble, Slate Physical Properties of Metamorphic Rocks •Layers look like ribbons •Crystals What are the processes that form metamorphic rock? Heat (caused by magma) •Temperatures high enough to change its structure but not to melt it. •Heat can change sedimentary, igneous, or another older metamorphic rock. Pressure - Caused by intense collisions and friction of tectonic plates and pressure from overlying rock layers. •Deep under the Earth’s surface. •Pressure can change sedimentary, igneous or another older metamorphic rock. Igneous Rock •Formed when lava or magma harden. •Found near volcanoes or fissures •Ex. Basalt, Obsidian, Granite Physical Properties of Igneous rock Fast Cooling Slow Cooling Glassy Large crystals Holes where gas was trapped Many colors What are the processes that form Igneous rock? Melting •Caused by increase in temperature in rock deep below the surface of Earth •Caused by friction between crustal plates Lava –molten rock material on Earth’s surface. Magma – molten rock material under Earth’s surface. What are the processes that form igneous rock? Cooling and Hardening •Melted rock turns solid. •Slow cooling happens below Earth’s surface as magma cools forming large crystals. Ex. granite •Fast cooling happens on the Earth’s surface as lava cools forming small crystals. Ex. obsidian, basalt, pumice Video Resource: https://drive.google.com/file/d/0BxOms4hIDvR3TmxEcHJWV2xzTkU/view Similarities of Rocks and Minerals •Inorganic compounds (non-living) •Both can be classified by their chemical composition. •Solids •Naturally formed •Found around the world in many of the same places on Earth Rocks •Most commonly classified by how they form. 1.Sedimentary 2.Metamorphic 3.Igneous •Composed of more than one mineral. •No definite chemical composition. •No definite crystal structure. Minerals In addition to being inorganic, solid, and naturally formed like rocks, minerals also have: •A definite chemical composition. (amounts of elements present) •A definite crystal structure. (unique arrangement of atoms/molecules) Mineral Identification – Important Vocabulary 1.Color (green, red, yellow, blue, etc.) 2.Streak (Color of the streak across a streak plate) 3.Luster (Metallic or Non-Metallic) 4.Hardness (Mohs Scale) 5.Density (Specific gravity) 6.Breakage Pattern (Cleavage and Fracture) Color •Many minerals have distinctive colors, but they come in a variety of hues. •Color should never be used as the only test for identifying a mineral. Streak •The color a mineral displays in a finely powdered form •Might be completely different from the color of the mineral itself •To determine the streak, rub the mineral across a piece of unglazed porcelain know as a streak plate. Luster •The way a mineral’s surface reflects light. •Two types of luster •Metallic – shiny like a metal •Nonmetallic – several kinds 1. Glassy - quartz 2. Pearly - talc 3. Greasy - graphite 4. Silky – gypsum 5. Resinous - sulfur 6. Adamantine - diamond Hardness •One of the most reliable ways to identify minerals •Compares the resistance of a mineral to being scratched by 10 reference minerals •Called the Mohs Hardness Scale •Named after Friedrich Mohs, a German mineralogist, who developed the scale in 1812 Density •Defined as the amount of matter per unit volume •Density = mass divided by volume •In minerals, the term specific gravity is used in describing density. In this way minerals can be compared and identified. Cleavage •Refers to the way some minerals break along certain lines of weakness in their structure Mica is a good example. Fracture •A description of the way a mineral tends to break •Some different types of fracturing 1. Conchoidal – smooth curve 2. Hackly – sharp jagged edges 3. Uneven – rough and irregular 4. Fibrous – shows fibers Gemstones Some minerals are cut to become precious gemstones.
Earth’s Crust
•The outer layer of the Earth •Similar to the skin on an apple (thinnest layer) •Made up of both continental (land)and oceanic crust(under the ocean) 5-50 km thick Oceanic Crust •A thin layer of crust that overlies the ocean basins •More dense than continental crust •Mostly basalt rock •Thinner that continental crust. (5-10km) •Younger (newer) than continental crust Continental Crust •Layer of rock which forms the continents •Less dense than oceanic crust •Mostly granite •Thicker that oceanic crust •Older than oceanic crust Lithosphere •Solid outer section of the Earth, which includes the crust (rocky layer) Also, includes the cool, dense, rigid upper part of the mantle Asthenosphere •Solid part of the upper mantle •Weaker, less rigid (plasticity - like silly putty) •Crust moves over the plastic-like asthenosphere •These plates crash into each other. Here the oceanic crust is subducting under the continental crust which creates volcanoes. Mantle •Largest layer of the Earth •Under the crust about 2,890km •Composed of silicate rocks rich in magnesium and iron •Intense heat causes the rocks to rise and then cool and sink. •The process is called convection, which causes the crust to move. Average temperature 3000o Outer Core •Liquid layer 2,300 km thick, second largest •Composed of liquid iron and nickel •Lies between inner core and mantle •Because the magma moves around the inner core, Earth’s magnetic field is created. •Average temperature 4000o -5000o Inner Core •A solid ball of metal •1,250 km thick •Made of solid nickel and iron •So hot it melts everything in the outer core •Spins at a speed faster than the Earth rotates •Densest layer of the Earth •Average temperature 5000o -6000o What are seismic waves? •Waves of energy caused by earthquakes and other rock movement •Travel through some layers of the Earth •Recorded with seismographs • Seismic waves are used to determine which layers of the Earth are solid or liquid. •Some seismic waves cannot pass through certain layers giving us a clue to the layers composition.
Continental Drift Theory
Alfred Wegener developed the theory that the continents drift. At the time he did not know the mechanism that made this happen. Sea-Floor Spreading Harry Hess discovered that magma was rising on the sea floor causing it to spread. The hot magma rising in the mantle caused the spreading on the sea floor and the large pieces of crust (tectonic plates) to move. Theory of Plate Tectonics These two theories lead to the Theory of Plate Tectonics. Plate Tectonics is the theory that Earth's outer crust (lithosphere) is divided into several plates that glide over the plastic-like and less ridged asthenosphere (upper mantle). What is the engine that moves the plates? Convection Currents •Transfers energy in the mantle •Causes the hotter magma in the mantle to rise •Causes the cooler magma in the mantle to sink Continental Crust •Layer of rock which forms the continents •Also forms shallow sea beds close to shore (continental shelf) •Floats on top part of the mantle (asthenosphere) •Older than oceanic crust, mostly granite rock •Thicker and less dense than oceanic crust Oceanic Crust •A thin layer of crust that underlies the ocean basins. •Consists mainly of basalt. •Younger than continental crust. •More dense than continental crust. What happens at plate boundaries? Plates do one of 3 things. 1.Converge (colliding or coming together) 2.Diverge (dividing or moving apart) 3.Transform (sliding past each other) Divergent boundaries – dividing or moving apart •Two oceanic crusts diverge and create a mid-ocean ridge (mountains under the ocean). •This process is call sea-floor spreading. •New crust is created. Divergent boundaries – dividing or moving apart •Two continental crusts diverge and create a rift valley. •New crust is created. •Example is the Great Rift Valley in Africa •Over millions of years water will eventually fill the valley. Transform boundaries •Plates slip sideways past each other creating earthquakes. •Crust is neither created or destroyed. •Many of these boundaries are found on the sea floor. •The most famous transform boundary is the San Andreas fault in California. What happens when plates converge or collide? •Continental/Continental = folded mountains (Himalayas). •Continental/Oceanic = volcanoes form (Cascades in Oregon and Washington) •Oceanic/Oceanic = Volcanic arc of islands form(Aleutian Islands in Alaska) Converging boundary -continental/continental boundary. •Two continental crusts collide and push against each other. •This pressure causes both plates to rise creating folded mountains. •Not a subduction zone Converging boundary - continental/oceanic boundary •The ocean crusts goes below the continental crust because its more dense. •Volcanoes form on the continent. •A trench forms at the place when the plates collide. •Subduction zone Converging boundary - oceanic/oceanic boundary •Two oceanic crusts collide and push against each other. •The older crust goes below the other one and creates a volcanic arc of islands. •Subduction zone Ring of Fire •A long chain of volcanoes that surround the Pacific Ocean. •One of the most geologically active area on Earth. •Site of frequent earthquakes and volcanic eruptions. •Caused by plate boundaries converging, diverging and transforming. Science 8: Whitetail Survival in the winter through adaptation and genetics. Students will create a slide show informing the audience how whitetail deer adapt to northern climates. (adaptations, behaviors, genetics & phenotype's) Presentations will begin on Thursday (10/11/18). http://www.pbs.org/wgbh/nova/evolution/evolution-action-salamanders.html
Evolution of Salamanders in California Video Archimedes
•287BC -212BC •Greatest mathematician and scientist of antiquity •Discovered method to help determine the volume of irregularly shaped objects The Archimedes’ Principle •Noticed when he stepped into his bath the water level rose. •Understood that the volume of water displaced must be equal to the volume of the part of his body he submerged. Volume •The amount of space an object takes up. •Measured with a graduate. •Units - liter, milliliters Displacement The difference between the initial volume (110ml) and the volume after an object is submerged (175 ml). V = V2 – V1 •Initial volume – V1 = 20 ml •Final volume – V2 = 23 ml •Volume of object V = 3 ml Mass •The amount of matter in an object. •Measured with a triple beam balance or a scale. •Units – grams, milligrams Density •Measure of how compact a substance is in a given volume. •The more molecules in a given volume the greater the density. •The fewer molecules in a given volume the less the density. How do you calculate density? Density = Mass/Volume Units – g/ml or g/cm3 What careers may use density? •Geologist - to identify minerals. •Chemical Engineers - to identify liquids and other substances. •Ship builders -to determine if ship will float. |
Erik E. Mason
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