Physical Geology The Rock Cycle Weathering Erosion Soil Formation Geohazards

Rock- mixture of minerals, volcanic glass, organic matter, or other materials Rock Cycle- model showing processes that create and change rock 1.) Sedimentary- changed by heat and pressure into metamorphic rock 2.) Metamorphic- can melt and cool to form igneous rock 3.) Igneous- rock can be broken into fragments that may later form sedimentary rock Conservation of matter- rock cycle never destroys elements of rocks but merely distributes them. James Hutton- recognized the rock cycle in 1788 by observing Siccar Point, Scotland Rock Cycle

Siccar Point, Scotland

Interactions among Earth’s water, air, land, and living things can cause rocks to change from one type to another. Continuous processes that cause rocks to change their make up Changes in rock occur over long periods of time Rock Cycle

Igneous Rocks Igneous rocks- form from magma found deep under Earth’s surface Form from cooling and crystallization of magma (molten rock beneath Earth’s surface) or lava (on Earth’s surface) “Fire-Formed Rocks” (Ignis=fire)

Rock Cycle Igneous Rocks Cooling rates influence the texture Quick cooling = fine grains Slow cooling = coarse grains Classified by: Texture - Intrusive vs. Extrusive Chemical Composition - Mafic vs. Felsic “Fire-Formed Rocks” (Ignis=fire)

Rock Cycle Igneous Rocks Intrusive- (interior) magma trapped below the surface forms large-grained rock when it cools Extrusive- (exterior) magma cooling quickly at or near Earth’s surface forms small- grained rock, or no crystals (glass or porous texture)

Rock Cycle Igneous Rocks Rock Composition  Felsic Dominated by silicon and aluminum (SiAl) Usually light in color Characteristic of continental crust Forms a stiff (viscous) lava or magma Rock types include: granite & rhyolite  Intermediate Intermediate in composition between felsic and mafic Rock types include: Andesite & Diorite

Rock Cycle Igneous Rocks Rock Composition  Mafic (or basaltic) Usually dark in color (dark gray to black) Forms a runny (low viscosity) lava Characteristic of Earth's oceanic crust, Hawaiian volcanoes Rock types include: basalt, gabbro, diabase  Ultramafic Rarely observed on the Earth's surface Believed to be major constituent of Earth's mantle Rock types include: peridotite

Rock Cycle Igneous Rocks Mafic- HOTTER FAST moving THIN fluid HIGH metal DARK color MORE dense Magma Type or Chemical Composition Felsic COOLER SLOW moving THICK fluid HIGH silica LIGHT color LESS dense

Rock Cycle Igneous Rocks Basaltic (mafic)- extrusive Dark-colored and dense Contain iron and magnesium but very little silica Basaltic lava flows freely from a volcano Granitic (felsic)- intrusive Contain more silica and less iron and magnesium Granitic magma is thick and stiff Andesitic- extrusive More balanced composition of minerals and density than basaltic or granitic Magma Type

Rock Cycle Igneous Rocks Rock Texture  Coarse grain (visible) – forms due to slow cooling of magma underground, composed of large crystals (e.g. granite, diorite, gabbro)  Fine grain – forms due to rapid cooling of lava at Earth's surface, composed of tiny crystals (e.g. basalt, rhyolite, andesite)  Porphyritic- Mixture of grain sizes caused by mixed cooling history; slow cooling first, followed by a period of somewhat faster cooling.

Rock Cycle Igneous Rocks Rock Texture  Glassy – forms as lava cools very rapidly at Earth's surface, in a matter of seconds or a few minutes. (e.g. obsidian)  Pyroclastic – forms as an explosive volcanic eruption mixes fragments of the volcano with hot ash in the atmosphere. (e.g. tuff)  Vesicular – holes or cavities as a result of gas expansion (bubbles) that occurs during volcanic eruption (e.g. scoria, basalt)  Frothy – forms as gas-charged lava cools very rapidly at Earth's surface. (e.g. pumice)

Rock Cycle Igneous Rocks

Rock Cycle Igneous Rocks A batholith is a great mass of igneous intrusive rock that forms from cooled magma deep in the Earth's crust. They are formed when multiple plutons converge to form a huge expanse of granite rock. Sierra Nevada Batholith in Yosemite National Park

Rock Cycle Igneous Rocks A vein is at the end of the crystallization process when mineral rich fluid fills voids and cracks -Forms gold or other rare minerals -Pegmatites: extremely large grained minerals (gem stones) -Kimberlites: found in rare ultramafic rock, extremely deep and under high pressure (diamonds)

Rock Cycle Metamorphic Rocks Metamorphic Rock- changed by temperature, pressure, and hot fluids

Rock Cycle Metamorphic Rocks 1.) Heat and pressure result from one layer of rock on top of another layer. - temperature and pressure are great enough to melt rock, forming magma - pressure alone flattens mineral grains in rocks without melting them - as pressure and temperature continue to increase over time, one type of rock can change into several different metamorphic rocks

Rock Cycle Metamorphic Rocks 2.) Hot, water-rich fluids can move through rock, chemically changing it

Rock Cycle Metamorphic Rocks Classification of metamorphic rocks- by composition and texture 1.) Foliated texture- mineral grains flatten and line up in parallel layers or bands 2.) Non-foliated- mineral grains grow and rearrange but do not form layers Animation

Rock Cycle Sedimentary Rocks Mostly found on the exposed surface of Earth Rock fragments, mineral grains, and bits of plants and animal remains moved by wind, water, ice or gravity are called sediments Sedimentary rocks form in layers

Rock Cycle Sedimentary Rocks - Classified by what they were made of and how they were formed - Detrital sedimentary rocks- made from broken fragments of other rocks 1.) compaction- layers of small sediments stick together because of pressure 2.) cementation- water and other minerals move through open spaces between larger sediments, gluing them together 3.) granular texture 4.) named according to size and shape of sediments a.) size can be large like gravel or small like clay b.) well-rounded or have sharp angles

Rock Cycle Sedimentary Rocks - Chemical sedimentary rocks- non-clastic rocks formed when dissolved minerals came out of solution 1.) Limestone forms from calcite, which was calcium carbonate in solution 2.) Rock salt forms from halite, which was salt in solution -Organic sedimentary rocks- made from remains of once- living plants or animals 1.) Chalk- made of microscopic calcite-shell remains of animals 2.) Coal- made of plant remains, chemically changed by microorganisms and compacts over millions of years

Process of Creating a Sedimentary Rock Step 1.) Weathering Step 2.) Erosion-movement of surface materials from one place to another. Step 3.) Deposition- sediments are laid down on the ground or sink to the bottoms of bodies of water. Step 4) Burial-sediments layer, pressure and temperature increase; results in bedding, or horizontal layering. Step 5) Lithification- Lithify comes from the Greek word lithos, which means “stone.” - physical and chemical process by which sediments are transformed into sedimentary rocks. - involves “compaction” and “cementation.”

Lithification Sediment Rock

28 REVIEW- Major Rock Groups Igneous Formed from a melt (molten rock) Plutonic (intrusive):slow cooling and crystallization Volcanic (extrusion): quick cooling at the surface Sedimentary Formed at the Earth’s surface Clastic/Detrital (Mineral Fragments or grains, clays) Chemical (crystalline chemical/biochemical precipitates) Metamorphic Changed by pressure, temperature and fluids.

MAGMA

30 MAGMA Crystallization IGNEOUS

31 MAGMA IGNEOUS Plutonic Crystallization

32 MAGMA Volcanic IGNEOUS Plutonic Crystallization

33 MAGMA Volcanic IGNEOUS Plutonic Uplift Crystallization Weathering

34 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT Uplift Crystallization Weathering SEDIMENT

35 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY Uplift Crystallization Weathering Erosion Transport Deposition

36 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY Uplift Crystallization Weathering Erosion Transport Deposition

37 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Crystallization Weathering Erosion Transport Deposition

38 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition Can you see any shortcuts?

39 MAGMA Volcanic IGNEOUS Plutonic SEDIMENT SEDIMENTARY METAMORPHIC Uplift Burial Increased P&T Melting Crystallization Weathering Erosion Transport Deposition

Forms of Energy that Drive Cycle 1) Heat-creates magma, causes metamorphism 2) Mechanical (gravitational potential) energy-ability of sediments to move downhill, plate motion due to gravity, metamorphism occurs as a result of plate motion