Geology Chapter 15

Geology The science devoted to the study of dynamic processes occurring on the Earth’s surface and in its interior

Essential Question #1 What are the characteristics of the three major concentric zones of earth?

Three Concentric Zones Core – innermost zone Extremely hot Solid inner part surrounded by liquid molten material Mantle – middle zone Outermost part is solid rock Asthenosphere = inner part made of hot partly melted pliable rock that flows Crust – outermost zone Continental crust Oceanic crust

Earth’s Crust and Upper Mantle Our knowledge of the earth’s interior comes mostly from indirect evidence such as density measurements, seismic (earthquake) wave studies, measurements of interior heat flow, lava analysis, and research on meteorite composition. Lithosphere = Crust and outermost Mantle

Tectonic plate Mantle Hot outer core Inner core Spreading center Collision between two continents Oceanic tectonic plate Oceanic tectonic plate Ocean trench Plate movement Plate movement Tectonic plate Oceanic crust Oceanic crust Subduction zone Continental crust Continental crust Cold dense material falls back through mantle Material cools as it reaches the outer mantle Hot material rising through the mantle Mantle convection cell The earth’s crust is made up of a mosaic of huge rigid plates, called tectonic plates, which move around in response to forces in the mantle. Mantle Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Hot outer core Inner core Fig. 15-3, p. 337

Essential Question #2 How does the movement of tectonic plates shape the earth’s surface and other zones? Internal Processes = driven by heat from the earths interior

Tectonic Plates Convection cells (currents) in the mantle move large volumes of heat and rocks in loops, causing the movement of large rigid plates (lithosphere) on the earth’s surface. Tectonic plates composed of lithosphere, continental crust / oceanic crust + outermost part of mantle. Move at about the rate that fingernails grow; imperceptible.

Tectonic Plate Boundaries The extremely slow movement of the tectonic plates causes them to grind into one another. Convergent – push two plates together Divergent – spread plates apart (oceanic) Transform – plates slide past each other

Tectonic Plate Boundaries Convergent Plate Boundaries Subduction - Continental plate usually pushes oceanic plate down into mantle Forms a trench in ocean & mountains on land Divergent Plate Boundaries As oceanic plates spread apart, molten rock (magma) pushes up the cracks forming ocean ridges Transform Faults Plates slide and grind past one another along a fracture (fault) in the lithosphere Mostly in oceans San Andreas Fault , CA

Major Tectonic Plates & Boundaries

Volcanos Often form along the boundaries of tectonic plates where magma can escape in the form of lava Volcanic eruptions releases lava rock, hot ash, liquid lava, and gases such as water vapor, carbon dioxide and sulfur dioxide. Large eruptions can alter climate for extended periods of time (cooling effect). Benefits include land formation and increased soil fertility.

Ring of Fire Huge ring of volcanic and seismic activity Includes 452 volcanos; over 75% of world’s active and dormant volcanos About 90% of the world’s earthquakes & 81% of the world’s largest earthquakes occur here Around the Ring of Fire, the Pacific Plate is colliding with and sliding underneath other plates. This process is known as subduction and the volcanically and seismically active area nearby is known as a subduction zone. There is a tremendous amount of energy created by these plates and they easily melt rock into magma, which rises to the surface as lava and forms volcanoes.

Earthquakes Colliding plates create tremendous pressures in the crust Earthquakes occur when stresses cause rocks to suddenly shift and break, forming faults Abrupt movement of faults release stored energy in the form of seismic waves, which move in all directions through the surrounding rock Focus = place where an earthquake begins Epicenter = place on the surface directly above the focus Severity measured in magnitude of seismic waves causing the ground to move (shake). Measure using instrument called seismograph.

Earthquake in Haiti – January 2010 7.0 Magnitude, followed by at least 52 aftershocks 4.5 or greater Over 220,000 dead; damaged 250,000 residences & 30,000 commercial buildings Despite humanitarian aid efforts, over 370,000 people still without homes today

Ocean Earthquakes & Tsunami’s Tsunami = a series of large waves generated when part of the ocean floor suddenly rises or drops

Indian Ocean Tsunami - 2004 9.15 Magnitude earthquake on ocean floor generated waves as high as 100ft Killed ~228,000 people in Indonesia, Thailand, Sri Lanka, South India & Eastern Africa Photos show Banda Aceh Shore near Gleebruk in Indonesia

Japan Tsunami - 2011 9.03 magnitude earthquake on ocean floor generated waves as high as 133ft Over ~16,000 reported dead/missing Estimated economic cost $235 billion (US) – costliest natural disaster in world history https://www.youtube.com/watch?v=av1Ieq0q06Q Meltdown of Fukushima Nuclear Power Plant as a result of the Tsunami became the worst nuclear disaster in world history (level 7 meltdown). Worse than Chernobyl.

How do physical, chemical and biological weathering generate soil? Essential Question #3 How do physical, chemical and biological weathering generate soil? External Processes = based directly or indirectly on energy from the sun or gravity

Weathering The physical, chemical, and biological processes that break down rocks and minerals into smaller particles that help build soil.

Weathering Physical (Mechanical) Weathering Chemical Weathering Large rock broken down into smaller pieces Chemical Weathering One or more chemical reactions slowly dissolve the minerals in rocks Biological Weathering Conversion of rocks or minerals into smaller particles through the actions of living things

Parent material (rock) Biological weathering (tree roots and lichens) Chemical weathering (water, acids, and gases) Physical weathering (wind, rain, thermal expansion and contraction, water freezing) Physical, chemical, and biological processes can weather or convert rock into smaller fragments and particles. It is the first step in soil formation. Particles of parent material Fig. 15-6, p. 340

Erosion The process by which material is dissolved, loosened, or worn away from one part of the earth’s surface and deposited elsewhere Mostly caused by flowing water, rain, wind, and human activities that destroy vegetation that holds soil. Glaciers can also cause erosion.

Mass Wasting When rock and soil become detached from underlying material and move downhill under the influence of gravity Rockslides, landslides, and mudslides.

Essential Question #4 What are the three classes of rocks, and how are they recycled by the rock cycle?

Rock A solid combination of one or more minerals that is part of the earth’s crust

3 Types of Rock Igneous Sedimentary Metamorphic Forms when molten rock (magma) wells up from the earth’s upper mantle, cools, and hardens Sedimentary Forms from sediment produced when existing rocks are weathered and eroded into small pieces Compaction (pressure) + Cementation (minerals seeping through sediment deposits) bind particles forming rock Metamorphic Forms when a preexisting rock is subjected to high temperatures / pressures, chemically active fluids, or a combination Igneous forms the bulk of earth’s crust, although it’s often covered by sedimentary rock or soil. Main source of many metal and nonmetal mineral resources.

Erosion Transportation Weathering Deposition Igneous Rock Granite, pumice, basalt, lava rock Sedimentary Rock Sandstone, limestone, shale, dolomite, bituminous coal Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) The rock cycle is the slowest of the earth’s cyclic processes. The earth’s materials are recycled over millions of years by three processes: melting, erosion, and metamorphism, which produce igneous, sedimentary, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or can be recycled within its own class. Melting Metamorphic Rock Slate, marble, gneiss, quartzite Fig. 15-8, p. 343

Soil: A Renewable Resource Chapter 3

What is soil and why is it important? Essential Question #5 What is soil and why is it important?

Soil A thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, and billions of living organisms (most of them microscopic decomposers) Soil is a renewable resource that is renewed very slowly (100’s to 1000’s of years)

Ecological Services of Soil Supply nutrients to producers Cleanses & stores water Important in biogeochemical cycling Decomposes organic matter Helps control climate by sequestering carbon Habitat for soil organisms Scientific research - antibiotics

Economic Services of Soil Supports agriculture industry Food, feed, fiber, fuel, etc Provides food security Stores solid waste Foundation for cities and towns

Soil & Human Civilization Human activities have accelerated natural soil erosion since the beginning of agriculture Mismanagement turns soil into a nonrenewable resource Sophisticated civilizations such as the Mayans, Easter Island, Harappan (India) ended as a direct result of mismanaging soil The Norse people who settled Greenland survived for 450 years before destroying the vegetation and soil that supported them. Sumerian civilization (4th century BC) collapsed mostly because long-term irrigation led to salt buildup in its soils and declining food productivity. Early settlers ecologically devastated Iceland, but the people learned from their mistakes & now have one of the world’s most environmentally sustainable countries and a prosperous economy.

Essential Question #6 What are the three sizes of particles that compose soils, and how do they determine soil texture?

Soil Particle Size Sand Largest Silt Medium Clay Smallest

Physical Properties of Soils Soil Texture Relative proportions of sand, silt & clay particles in a soil Measured using Soil Triangle LOAM Soil = BEST for plant growth Permeability The rate at which water moves through soil Porosity – the amount, size and arrangement of pores between particles Water Holding Capacity Ability of pores to hold water for plant use Soil Compaction - destoys the quality of the soil because it restricts rooting depth and decreases pore size. The effects are more water-filled pores less able to absorb water, increasing runoff and erosion, and lower soil temperatures.

Soil Texture Triangle

Chemical Properties of Soil Soil Salinity and Interpretation Chemical Properties of Soil Conductivity (mmho/cm) Interpretation 4 or above Severe accumulation of salts. May restrict growth of many vegetables and ornamentals. 2 to 4 Moderatre accumulation of salts. Will not restrict plant growth, but may require more frequent irrigation. less than 2 Low salt accumulation. Will not affect plants. Nutrients Primary: Nitrogen (N), Phosphorus (P), Potassium (K) Secondary: Sulfur (S), Calcium (Ca), Magnesium (Mg) pH Affects availability of plant nutrients Optimal pH between 5.5 – 7.5 More acidic soils hold more toxic nutrients Affects soil organisms & nutrient cycling Salinity Salts come from irrigation water, fertilizers, composts & manure Dolomite lime, calcium carbonate, and wood ash can increase soil pH.

Microorganisms are the driving force for nutrient release to plants Organic Matter & Soil Microorganisms are the driving force for nutrient release to plants