GEO 120 1st EditionFinal Exam Study GuideExam 1Plate Tectonics: Big Ideas!1) The outermost layer of the Earth is broken up into tectonic plates.2) Tectonic plates move relative to each other.3) The boundary between two tectonic plates can be convergent (moving towards each other), divergent(moving away from each other) or transform (sliding past each other).4) The movement and interaction of tectonic plates helps to explain many of Earth's features.Oceanic Crust: Thinner, more dense (in subduction zones oceanic plates will slide under continental) Continental Crust: Thicker, less denseDivergent Plates: Plates moving apart from each other (most common in ocean plates) Continental rift: Creation of a divergent boundary on a continent1. Initial uplift from rising magma2. Stretching/faulting from rift (melting forms magma)3. Can lead to seafloor spreading (new ocean basin)4. Ocean widens from spreading (example: Atlantic ocean)Convergent boundary: Plates moving towards each other- Ocean- Continent: Ocean slides under Continental, subduction zone - Ocean- Ocean: One plate (the thicker/denser of the two) is subducted Continental Collision: 2 continental masses converging, produces huge mountain ranges- solidified magma in crust is present- deformation causes mountain beltsTransform boundary: Plates sliding against each otherEarthquakes: in belts and along mid-ocean ridges, trenches, and mountain beltsVolcanoes: not in plateaus, ocean-ocean divergent, ocean-continent convergentMountains: anywhere but transform boundariesThree driving forces of plate motion1. Gravity2. Slab pull- pulling (subducting) plate under3. Ridge push- force pulling each side of the divergent plate downPlates move 1-15cm a year (about as fast as fingernails grow)Earth Materials (minerals): 1) Minerals are the building blocks for rocks.2) Minerals have defined chemical compositions and internal structures, which give them their characteristics.3) Silicate minerals are the most common minerals in Earth's crust.4) The types of minerals present in a rock give us information about how that rock formed.5) Minerals have many uses in society.Characteristics that define a mineral; natural, inorganic, solid, ordered internal structure, and specific chemical compositionMineral characteristics that are used to identify minerals; crystal shape, cleavage, hardness, streak, luster, and effervescenceMajor classes of rock-forming minerals (key elements underlined): - Silicates- silica tetrahedron, SiO4- Carbonates- CO3 - Oxides- metal + oxygen, FeO4- Halides- metal + Halide, Nacl - Sulfates- SO4 - Sulfides- metal + sulfur, FeS2- Native metals- Metal by itself4) Know that silicates are the most common minerals in Earth's crust, and therefore Silica and Oxygen are the most abundant elements in Earth's crust.Basic structure of silicate minerals: - Single chains- 2 perpendicular plains (90 degree)- Double chains- 2 non perpendicular plains (60 and 120)- Framework- no cleavage (crystal structure example=Quarts)- Sheets- one dominant plainMost common silicate minerals: - Quartz- K-feldspar- Plagioclase feldspar- Muscovite- Biotite- Amphibole- Pyroxene- Olivine.Felsic:- Lighter in color- No Fe, Mg- Melt first (@lower temps)- Crystalize lastMafic:- Darker colored- Has Fe, Mg- Melt last (at higher temps)- Crystalize lastIgneous rocks: 1) Igneous Rocks are formed from the cooling of molten rock.2) Igneous Rocks are classified by their composition and texture. 3) The composition of an igneous rock provides information about the source and evolution of the magma that formed it.4) The texture of an igneous rock provides information about its cooling history.5) Melting of rocks requires: heating, release of pressure, addition of water or some combination of the three.6) Mafic minerals melt/crystalize at higher temperatures than felsic minerals.7) The mechanism of melting and source of magma is different at different tectonic settings.Partial crystalizing: The rocks will be more mafic because the felsic will melt out first (this also means the magma will be more felsic) Ways to melt a rock:- Decompression - Heat- Addition of waterAs a rule: higher temperature and pressure will turn solid rock into liquid magmaTextures- Aphanitic: Fine-grained (small crystals not distinguishable by naked eye)- Porphyritic: Large and small crystals (first slow cooling and then fast)- Phaneritic: Coarse-grained, crystals seen by the naked eye (“spotted” for example: granite) - Glassy: cooled almost immediately (no time for crystals to grow)- Pegmatic: very large crystals (more than 1 cm)- Vesticular: full of tiny “vessels” lightweightFelsic Intermediate Mafic UltramaficIntrusive (coarsely- crystalin)Granite Diorite Gabbro PeridotiteExtrusive (Finely-crystalin)Rhyolite Andesite BasaltRapid cooling- creates smaller crystals Slow cooling- creates larger crystals Extrusive- Cooled outside of the crustIntrusive- Cooled inside the crust (has more growth time/has bigger crystals)Mid Atlantic ridge:- Cause of melting- Decompression- Sources of Magma- Mantle rising- Types of Magma- Mafic- Types of rock- Basalt, GabbroSubduction zone:- Cause of melting- Heating + addition of water- Sources of Magma- Mantle and continental crust- Types of Magma- Mafic, intermediate, and felsic - Types of rock- Granite, Andesite Hot Spot:- Cause of melting- Decompression and heating- Sources of Magma- Mantle and oceanic crust- Types of Magma- Mafic- Types of rock- BasaltVolcanoes:1) Volcanoes are places where magma, and other volcanic products such as ash and gasses, erupt on to Earth's surface.2) The shape of a volcano and the style of its eruptions are controlled by the composition of the magma and its gas content.3) More viscous magmas with higher gas content are more explosive.4) We can make predictions about a volcano's characteristics and eruption style based on its tectonic setting and magma composition.5) Volcanoes pose large risks to communities located near them. 6) Volcanoes are monitored closely and the risk of volcanic hazards are assessed by geologists and emergency planners. Eruption styles: (increasing explosivity)1) Lava flows2) Lava fountains 3) Eruption columnsViscosity:-resistance to flow High viscosity- Lava piles up - Lower temp- Abundant silica chains - More gas-more explosive Low viscosity- Lava spreads out - Higher temp- Fewer silica chains- Less gas-less explosiveFelsic magma- Gas bubbles cant escape easily, high pressure, explosive eruptions, high