Earth’s Geological Cycle

What Are the Earth’s Major Geological Processes? Main Processes: Plate Tectonics Rock Cycle Soil Formation

The Earth’s Structure Earth’s Interior Core (Nickel & Iron) Mantle Inner Core (solid) Outer Core (liquid) Mantle Inner mantle (magma in motion) Asthenosphere – outer part of mantle, flexible rock Outer mantle (solid) Crust Continental crust Oceanic crust: 71% of crust, DENSE LITHOSPHERE

Major Features of the Earth’s Crust and Upper Mantle

Another look at

The Earth Beneath Your Feet Is Moving Why do the tectonic plates move? Convection cells, or currents Liquid rock is heated near the core and rises, cooler rock falls = convection currents INSIDE the earth

Types of Boundaries Three types of boundaries between plates Divergent plates Magma Oceanic ridge Convergent plates Subduction zone Trench Volcano Transform fault; e.g., San Andreas fault

Collision between two continents Spreading center Ocean trench Oceanic tectonic plate Oceanic tectonic plate Plate movement Collision between two continents Plate movement Tectonic plate Subduction zone Oceanic crust Oceanic crust Continental crust Continental crust Cold dense material falls back through mantle Material cools as it reaches the outer mantle Mantle convection cell Hot material rising through the mantle Figure 14.3 The earth’s crust is made up of a mosaic of huge rigid plates, called tectonic plates, which move very slowly across the asthenosphere in response to forces in the mantle. See an animation based on this figure at CengageNOW™. Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Mantle Hot outer core Inner core Fig. 14-3, p. 346

The Earth’s Major Tectonic Plates

The San Andreas Fault as It Crosses Part of the Carrizo Plain in California, U.S.

The Geological Cycle: Some Parts of the Surface Build Up & Some Wear Down Internal geologic processes Generally build up the earth’s surface External geologic processes Generally wear down the earth’s surface Driven directly or indirectly by sun and gravity Weathering Physical, Chemical, and Biological Erosion Wind Flowing water Human activities Glaciers

Volcanoes Release Molten Rock from the Earth’s Interior 1980: Eruption of Mount St. Helens Worst volcanic disaster in US History 1991: Eruption of Mount Pinatubo Largest eruption of 20th century Cooled the earth’s temperatures for 15 months 5 largest volcanic eruptions in recent history Benefits of volcanic activity

Mount Pinatubo

Creation of a Volcano

Measuring Earthquakes There are more than one million earthquakes a year!! Most are too small to be felt Richter scale Insignificant: <4.0 Minor: 4.0–4.9 Damaging: 5.0–5.9 Destructive: 6.0–6.9 Major: 7.0–7.9 Great: >8.0 Largest ever recorded: 9.5 in Chile on May 22, 1960

Areas of Greatest Earthquake Risk in the United States

Areas of Greatest Earthquake Risk in the World

Major Features and Effects of an Earthquake

Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis Tsunami, tidal wave Caused by movement of the ocean floor Can travel as fast as a jet plane across open ocean Detection of tsunamis DART (http://nctr.pmel.noaa.gov/Mov/DART_04.swf) Pressure recorders on the ocean floor measure changes in pressure (increased waves) December 2004: Indian Ocean tsunami Magnitude of 9.15 Role of coral reefs and mangrove forests in reducing death toll

Formation of a Tsunami and Map of Affected Area of Dec 2004 Tsunami

Shore near Gleebruk in Indonesia before and after the Tsunami on June 23, 2004 http://oar.noaa.gov/podcast/2009/video/NOAA_TsunamiForecastingNoMusic.mov

Gravity and Earthquakes Can Cause Landslides Mass wasting Slow movement Fast movement Rockslides Avalanches Mudslides Increased due to human activities Forest Clearing Road building Crop Growing Building houses on steep slopes

Active Figure: Geological forces

Active Figure: Plate margins

The Cycling of Earth’s Rocks The three major types of rocks found in the earth’s crust—sedimentary, igneous, and metamorphic—are recycled very slowly by the process of erosion, melting, and metamorphism.

The crust is composed of rocks & minerals Minerals- elements or inorganic compounds that occur naturally in the earth’s crust as a solid with a regular internal crystalline structure Ex: gold, diamond, silver, salt, quartzite Rocks – a solid combination of one or more minerals found in the earth’s crust Example: Granite = mica + feldspar + quartz

Classifying Rocks There are three broad classes of rocks, based on formation Sedimentary (deposited) Igneous (volcanic) Metamorphic (heat & pressure) 30

There Are Three Major Types of Rocks (1) Sedimentary Sandstone Shale Dolomite Limestone Lignite Bituminous coal 31

There Are Three Major Types of Rocks (2) Igneous (form the bulk of the earth’s crust) Granite Lava rock

There Are Three Major Types of Rocks (3) Metamorphic Anthracite Slate Marble 33

The Earth’s Rocks Are Recycled Very Slowly Rock cycle Slowest of the earth’s cyclic processes

Heat, pressure, stress Magma (molten rock) Erosion Transportation Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Figure 14.13 Natural capital: the rock cycle is the slowest of the earth’s cyclic processes. Rocks are recycled over millions of years by three processes: erosion, melting, and metamorphism, which produce sedimentary, igneous, 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 (Concept 14-2). Question: What are three ways in which the rock cycle benefits your lifestyle? Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 14-13, p. 354

SOIL PPT STARTS HERE

Soil Formation The Importance of Soil All life depends on the thin top layer of soil covering the earth’s surface. Topsoil provides: Support Water Air Nutrients

Weathering: Biological, Chemical, and Physical Processes

Weathering: Breakdown of Rock near the Surface Mechanical Geological Activity – abrasion Glacial Activity Expansion of ice Effects of Temperature

Erosion – by wind

Erosion – by water

Glacier Receding

Wedging - Frost

Weathering: Breakdown of Rock near the Surface Chemical Alteration Carbon dioxide, sulfur dioxide and various nitrogen compounds from the air form acids when dissolved in water. These acids may react with the rock and increase breakdown.

Chemical Weathering

Chemical Weathering

Weathering Breakdown of Rock near the Surface Organic Processes Wedging – Plant Roots

Wedging - Roots

What Determines Soil Type Climate Vegetation Drainage Time Parent Material Residual - Transported Least Important Factor for Mature Soils

Soil Composition

What determines soil type? Young Soils/Immature Soils Strongest Influence Is Parent Material Mature Soils Strongest Influences: Climate, Vegetation, Drainage

Soil Formation and Generalized Soil Profile 53

Soil Horizons and Profiles Soil Profile Suite of Layers at a Given Locality Soil Horizons Layers in Soil Not Deposited, they are Zones of Chemical Action Layers (horizons) of mature soils O horizon: leaf litter A horizon: topsoil B horizon: subsoil C horizon: parent material, often bedrock

Principal Soil Horizons O - Organic (Humus) Often Absent A – Leaching K, Mg, Na, Clay Removed B – Accumulation Absent in Young Soils Distinct in Old Soils Al, Fe, Clay (Moist) Si, Ca (Arid) C - Parent Material

Soils of the U.S.

Typical Soil Profile (Spodosol)

Ultisols – Georgia Clay

Active Figure: Soil profile

Soil Characteristics Physical Texture Porosity Permeability Humus Chemical pH *You need to know how to fix pH problems Nitrogen Phosphorous Potassium

Permeability – the degree to which the pores in the rock or soil are connected together so that water can move freely Porosity - the percentage of interconnected space in rock and soil that can contain water

Main Soil Textures Soil Type Texture Permeability Porosity Sand Gritty High Low Silt Smooth & Slippery Med Clay Sticky

Soil Formation vs. Soil Erosion Takes hundreds of years to form 1 cm (0.4 inches) of soil Soil erosion Blown away in weeks or months from plowing and clearing forests – any time we leave the topsoil unprotected 63

Topsoil Erosion Is a Serious Problem in Parts of the World Two major harmful effects of soil erosion Loss of soil fertility through depletion of plant nutrients in topsoil Water pollution in nearby surface waters where eroded soil ends up as sediment Kills fish, shellfish Clogs irrigation ditches, reservoirs, lakes, and boat channels Eroded soil may also be polluted with pesticides and fertilizers

Dust Bowl of the 1930’s

China’s Dust Storms - 2006

Soil Textural Triangle Practice Exercises % Sand % Silt % Clay Texture Name 75 10 15 sandy loam 10 83 7 _______________

Reduce Soil Erosion Soil conservation, some methods Terracing Contour planting Strip cropping with cover crop Alley cropping, agroforestry Windbreaks or shelterbeds Conservation-tillage farming No-till Minimum tillage Identify erosion hotspots 68

Figure 12.24 Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A). Fig. 12-24a, p. 302

Figure 12.24 Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A). Fig. 12-24b, p. 302

Figure 12.24 Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A). Fig. 12-24c, p. 302

Figure 12.24 Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A). Fig. 12-24d, p. 302

Solutions: Mixture of Monoculture Crops Planted in Strips on a Farm 73

Conservation Tillage Conservation-tillage farming: method of soil cultivation that leaves the previous year's crop residue on fields before & after planting the next crop No-till: involve planting crops directly into residue that either hasn't been tilled at all Minimum tillage: some residue has been removed, but at least 30 to 70% remains

No Till & Minimum Tillage Planting into corn residue (no till) Soybeans grown in striped rows between corn residue (minimum tillage)

Benefits of Conservation Tillage Environmental benefits Reduces soil erosion by 60%-90% from rain & wind Improves soil and water quality by adding organic matter as crop residue decomposes Conserves water by reducing evaporation Conserves energy due to fewer tractor trips Reduces air pollution from dust and diesel Crop residue provides food and cover for wildlife

Benefits of Conservation Tillage Practical benefits Fewer trips across the fields saves time and money (lowers fuel, labor and machinery maintenance costs) and reduces soil compaction that can reduce yields Optimizes soil moisture, enhancing crop growth in dry periods or on droughty soils