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UNIT: Inside Earth Geologists • Scientists that study the processes that create Earth’s features and the Earth’s History Forces That Shape Earth’s Surface: Destructive Forces • The forces that slowly wear away the Earth’s surface • Examples: Weathering and Erosion (Mass Wasting, Rivers, Glaciers, Wind, Waves) Forces that Shape the Earth’s Surface: Constructive Forces • Forces that build up the Earth’s surface • Examples: Earthquakes, plate tectonics, volcanoes, etc How do Scientists Know what is inside the Earth? • Scientists use indirect evidence to determine what is inside the Earth • earthquake waves (SEISMIC WAVES) help determine what is in the Earth • Seismic waves change speed or stop when they enter different materials • This shows that Earth is made of layers Earth’s characteristics change as you travel toward her center. • TEMPERATURE: increases with depth • PRESSURE: increases with depth Layers Within the Earth • The Earth possesses three main layers: • Crust, Mantle, and Core The Crust • Earth’s outermost layer • Made up of ocean crust-Basalt • Made up of continental crustgranite • Rigid rocky layer of Earth The Mantle • The second layer within the Earth • 5 to 40 Km below the surface • Asthenosphere: upper layer of the mantle that is “plastic” in nature • The plates that carry the continents “float” on the asthenosphere The Core • Made of two layers-the outer core and the inner core • Outer Core: liquid sphere of molten nickel and iron Inner Core: solid ball of nickel and iron Earth’s Magnetic Field • Earth acts as a magnet in space • It has both a North and South pole • caused by fluid movements in Earth’s liquid outer core causing the solid inner core to spin Inside Earth Chapter 1 Section 2: Convection Currents in the Mantle Heat Transfer • The movement of heat from warmer locations to cooler ones • 3 Types: – Radiation – Conduction – Convection 3 Types of Heat Transfer: Radiation • Transfer of heat through empty space • No direct contact between particles is required. Does not need a solid liquid or gas. • Example: Heat from a fire moving sideways, heat from the sun moving through space 3 Types of Heat Transfer: Conduction • The transfer of heat by collisions between atoms and molecules. Best in solids! • Example: a spoon becomes hot when in a pot of soup, burning your hand when you touch a curling iron 3 Types of Heat Transfer: Convection • Heat transfer through movement of hot fluids because of density differences. • heated particles begin to flow from one part of the fluid to another • Hot material=less dense = rises • Cooler material=more dense= sinks • Examples: Hot water circulating in a pot on the stove. Warm air circulating in a room. Convection in Earth’s Mantle • Magma is heated by the core, rises to the crust, cools, then again sinks to be reheated • This causes a Convection Current to form in the upper mantle as shown in the diagram below CHAPTER 1; SECTION 3: The Theory Continental Drift • all continents were once joined together in one single landmass scientists called: PANGEA “Continental Drift” Evidence For Continental Drift Landforms The continents fit together like a puzzle Fossils Climate The same fossils found on several different continents Tropical fossils were found in arctic areas Mountain ranges are the same on Different continents The same rocks and minerals are found at edges of continents Continents “Drifted” to their current locations…. CHAPTER 1; SECT. 4: Sea-Floor Spreading: 1 • The ocean floors are not smooth and featureless as once believed • Scientist now know that the ocean floor has a huge mountain range that encircles the globe called the MID-OCEAN RIDGE SYSTEM Sea-Floor Spreading: 2 -The Process– molten material rises from the mantle and erupts – The lava creates new rock at the ridge and pushes old rock to both sides of the ridge – Old Rock is destroyed (remelted) at trenches – This process is called SEA-FLOOR SPREADING Sea-Floor Spreading: 3 -diagram- Sea-Floor Spreading: 5 -Evidence to support it• Volcanic activity has been observed at the ridge system • Reversal of magnetic polarity are locked in rocks on either side of the ridge system at equal distances. • Drill samples from the ocean floor are the same age at equal distances from the ridge system Subduction at Deep-Ocean Trenches • Deep ocean trenches occur where ocean crust is thrust underneath continental crust • Subduction occurs where dense ocean crust is pushed under less-dense continental crust to be re-melted in the mantle • This process occurs over tens of millions of years • This process allows new crust to be created at the ridge systems and old crust to be re-melted; keeping the Earth the same size CHAPTER 1; SECTION 5: The Theory of Plate Tectonics • Explains: –Formation of Earth’s Crust –Movement of Earth’s Crust –Subduction (destruction) of Earth’s Crust Plate Boundaries • Edges of crustal plates • Transform Boundary: – Plates slip past each other in opposite directions (side to side) Ex: San Andreas Fault • Divergent Boundary: – Plates are moving away from each other – Forms Rift Valleys, mid-ocean ridge • Convergent Boundary: – Plates move toward each other and collide – Forms trenches and rift valleys Earth’s Plate Boundaries Prentice Hall, 2000 CHAPTER 2: SECT. 1: EARTHQUAKES • EARTHQUAKE: –A VIOLENT SHAKING OR TREMBLING OF THE EARTH’S CRUST THAT RESULTS FROM MOVEMENT OF ROCK BENEATH THE EARTH’S SURFACE Types of Stress in the Crust: -Shearing Stress• Stress: a force that can cause rock to change it’s shape or volume • Shearing Stress: pushes rock in two opposite, horizontal directions • Example: San Andreas Fault in California – One plate moves South and the other one moves North Types of Stress in the Crust: -Tensional• A force that pulls on the crust, stretching rock so that it becomes thinner in the middle. • This occurs when two plates move apart • Example: North East African Rift Zone Types of Stress in the Crust: -Compressional• Stress that squeezes rock until it folds or breaks • This occurs when one plate collides with another • Example: India and Eurasia; the Himalayan Mountains are continuing to grow due to compressional stresses Faults • Breaks in the Earth’s crust where movement occurs • Usually occur along plate boundaries Three Types of Faults • Strike-slip Faults: – Occur along transform boundaries; shearing stresses • Normal Faults: – Occur along divergent boundaries; tensional stresses • Reverse Faults: – Occur along convergent boundaries; compressional stresses Mountain Building • Over millions of year, stresses can turn flat land surfaces into towering mountains Mountains from Folding • Compressional stresses cause rocks to bend upward or fold • These folds can create alternating hills (anticlines) and valleys (synclines) Mountains from Faults • Faults can cause areas to be uplifted thousands of feet • Fault-Block Mountains: – Areas where paired normal faults uplift blocks of rock forming mountains – Ex: plateaus Chapter 2: Sect. 2: Measuring Earthquakes • Earthquake Focus: – The location within the Earth where rocks break releasing earthquake energy • Earthquake Epicenter: – The point on the Earth’s surface directly above the Focus; greatest damage here • Seismic Waves: – Three types of shock waves the are emitted from the focus of an earthquake; used for study Types of Seismic Waves • Primary Waves (P-waves): – First waves to arrive at a seismograph; compression and expansion; travel through solids and liquids. • Secondary Waves (S-waves): – Second waves to be recorded; move the ground up and down; back and forth – Travel through solids only • Surface Waves: – Very slow; cause severe ground movement; most damaging form of seismic waves Detecting Seismic Waves • Seismograph: – Device that records ground movements causes by seismic waves From Prentice Hall 2000 Rating Earthquake Strength • Richter Scale – Rating earthquake size using a Richter Seismograph – Works well for small, local earthquakes – Most widely used method for public reporting – Scale of 1 - 10 • Moment Magnitude Scale – Used most often by geologists – Works for all earthquakes – Takes amount of movement and the intensity into account – Much more accurate Locating an Epicenter • Collect P and S-wave data from three seismic monitoring stations • Calculate the difference in arrival times between P and S-waves • Determine the distance to the epicenter • Draw circles around all three stations with radii proportional to the distance • They will intersect at the epicenter! Earthquake Hazards • Liquefaction: – Ground shaking is amplified by loose soil; buildings sink • Aftershocks: – Smaller quakes that occur after a larger one • Tsunamis: – Tidal waves that occur when earthquakes occur under the ocean Making Buildings Safer • Choice of building location: – Locate buildings on shallow slopes, and on solid ground; bedrock is best • Base-isolated building: – A means of building where the foundation of a building is separated from the rest of the building by large springs or shock absorbers – This allows the ground to move but the building to remain stationary Inside Earth Chapter 3 Volcanoes Chapter 3: Sect 1: What is a Volcano? • A weak spot in the crust where molten material, magma, comes to the surface • Magma: underground liquid rock • Lava: liquid rock at the Earth’s surface Where are volcanoes found? • Ring of Fire: – A geographic region that rings the Pacific Ocean – Many volcanoes occur due to the many plate boundaries that exist in this region – Plate boundaries provide a weak spot in the crust that is necessary for volcano formation Hot Spot Volcanoes • A special volcano that is not located on a plate boundary, but in the center of a plate • Magma melts through the Earth’s crust to spill out onto the Earth’s surface • May be causes by a super-heated plume of magma (scientists are not sure) • Hawaii Chapter 3: Sect 2 Volcanic Activity What makes a Volcano Erupt? • Magma rises toward the Crust because it is hot and less dense than the solid rock around it, however, it gets trapped under the crust • Gases dissolved in the magma build up • Eventually, the gas must escape; and an eruption occurs • The escaping gas pushes the magma out Types of Eruptions: Quite Eruptions • Quiet Eruptions occur with a very fluid, low silica, low gas magma • Example: Mt. Kilauea, Hawaii • Lava slowly oozes out of the volcanic vent Types of Eruptions: Explosive Eruptions • Explosive eruptions occur with a more viscous (thicker), higher silica, high gas magma • Example: Mt. St. Helens, Washington; May 18, 1980 • Gas cannot escape the thick lava so it builds up and eventually explodes violently Mt. St. Helens after 1980 eruption Other Volcanic Activity • Hot Springs Homework Page 102; 1-4 Chapter 4: Sect. 1 Properties of Minerals • Mineral: – A naturally occurring, inorganic, solid, which a definite crystal structure, and a definite chemical composition Identifying Minerals • Scientists use a mineral’s characteristics to determine its identity • However, they never rely on just one characteristic because different minerals may have several characteristics in common Identifying Characteristics • Hardness: – The tendency of a mineral to be scratched – Mohs Hardness scale:1(softest) – 10(hardest) • Color: – Easily observed but not reliable for identification; many minerals are the same color • Streak: – Color of a mineral’s powder; very useful Identifying Characteristics Con’t • Luster: – How a mineral reflects light; metallic, nonmetallic, etc. • Density: – Each mineral has a characteristic density – Very useful for mineral identification • Crystal Shape: – Each mineral fits into a one of six crystal families; useful for classification Crystal Shapes of Minerals Identifying Characteristics Con’t • Cleavage and Fracture: – How a mineral breaks – Cleavage is breaking along flat surfaces – Fracture is breaking randomly • Special Properties: – Some minerals have unique characteristics – Fluorescence: glowing under UV light – Magnetism, radioactivity, etc. Chapter 4: Sect. 2 How do minerals form? • Crystallization from magma: – Molten magma cools, minerals slowly harden and settle out – Ex: feldspars • Crystallization from water: – Hot groundwater cools as it travels through the ground – Minerals crystallize and adhere to surrounding rock as the groundwater passes – Ex: quartz Chapter 5: Rocks • Rocks are a combination of 1 or more minerals GRANITE SANDSTONE Chapter 5: Sect. 1 Classification of Rocks • Geologists base rock classification on two things: – Texture: the size, shape, pattern, or lack of the individual grains in a rock – Mineral Composition: the actual mineralogy of the rock This helps to determine if the rock is Igneous, Sedimentary, or Metamorphic Chapter 5: Sect. 2: Types of Rocks: Igneous rocks • Igneous means “born of fire” • Extrusive igneous rocks: – Formed from lava at Earth’s surface – Cool very quickly; fine grained or no grains – Ex: basalt, obsidian • Intrusive igneous rocks: – Form from magma deep underground – Cool very slowly; coarse grained – Ex: granite, gabbros Chapter 5: Sect. 3 Types of Rocks: Sedimentary rocks • Form from compaction and cementation of sediments • 1. sediment is deposited, 2. compacted, 3. cemented, 4. rock • Clastic Rocks: made up of parts of other rocks • Only rocks with fossils • Ex: shale, sandstone, conglomerate Chemical Sedimentary Rocks • Sedimentary rocks that have crystallized out of a solution • Halite (rock salt), Limestone, gypsum • Form when bodies of water evaporate over long periods of time • Great Salt Lake, Utah: this occurs here today Chapter 5: Sect. 5 Types of Rocks: Metamorphic • Igneous or sedimentary rocks that are heated and squeezed • The minerals are rearranged but not melted • Foliated texture: – Minerals that are layered or banded in a metamorphic rock – Ex: gneiss or schist Granitegneissschist Chapter 5: Sect. 6 The Rock Cycle • Due to weathering, erosion, and deposition, rocks at the Earth’s surface are continually being created and destroyed • The Rock Cycle: – The processes on and inside Earth that change rock from one type to another – Ex: Granite(igneous) weathering/deposition sandstone (sedimentary) heat/pressure quartzite (metamorphic) The Rock Cycle Prentice Hall, 2000