4.14 sg

Chapter 14: Geology and Earth Resources

Page 1: Introduction

• Geology is the study of the Earth, its materials, processes, and history.

• Examines the physical structure of the planet and its resources.

Page 2: Our Earth is a Dynamic Planet

A Layered Sphere

• Core:

  • Interior composed of dense, intensely hot metal, primarily iron.

  • Generates a magnetic field surrounding the Earth.

• Mantle:

  • Hot and pliable layer surrounding the core.

  • Less dense than the core.

• Crust:

  • Cool, lightweight, and brittle outermost layer.

  • Floats on top of the mantle.

Page 3: Earth's Cross Section

• Continental Crust:

  • Thicker and less dense than oceanic crust.

• Oceanic Crust:

  • Thinner and denser than continental crust.

• Uppermost Mantle:

  • Rigid layer approximately 100 km thick.

• Asthenosphere:

  • Soft, ductile part of the mantle, approximately 200 km thick.

• Core Structure:

  • Inner core (solid) is about 6,370 km deep.

  • Outer core (semi-solid) at 2,900 km depth.

Page 4: Tectonic Processes

• Convection currents in the upper mantle break the crust into tectonic plates.

  • Plates move slowly across Earth’s surface.

• Ocean basins form where continents crack and separate.

  • Magma rises through cracks to form new oceanic crust in mid-ocean ridges.

Page 6: Earthquakes and Tectonic Activity

• Earthquakes result from plates grinding and jerking past one another.

• Mountain ranges arise at the collisions of tectonic plates.

  • Oceanic plates subduct beneath continental plates, melting into the mantle.

  • Deep ocean trenches characterize subduction zones.

Page 9: Geologic Time

Era and Periods

• Cenozoic Era:

  • Quaternary: First humans appear.

  • Tertiary: Rise of mammals following dinosaur extinction.

• Mesozoic Era:

  • Cretaceous: Extinction of dinosaurs; rise of flowering plants.

  • Jurassic and Triassic eras marked by the dominance of dinosaurs.

• Paleozoic Era:

  • Evolution of fish, reptiles, and first land plants.

• Precambrian:

  • Formation of Earth and earliest life forms; the majority of geologic time.

Page 11: Rocks and Minerals

• Definition of a Mineral:

  • Naturally occurring, inorganic, solid substance with a definite chemical composition and crystal structure.

• Rock Definition:

  • A solid aggregate of one or more minerals.

Page 12: Rock Types and the Rock Cycle

• Types of Rocks:

  • Igneous: Formed from solidified magma.

  • Sedimentary: Formed by the accumulation and compaction of sediments.

  • Metamorphic: Existing rocks altered by heat, pressure, and chemical processes.

• Rock Cycle: Cycle of formation, breakdown, and reformation of rocks.

Page 14: Igneous Rocks

• Most common rock type in Earth's crust.

  • Formed from solidification of magma when it cools.

  • Rapid cooling produces fine-grained rocks like basalt.

  • Slow cooling results in coarse-grained rocks like granite.

Page 15: Metamorphic Rock

• Formed from preexisting rocks altered by heat, pressure, and chemical action.

  • Notable examples include marble (from limestone) and slate (from shale).

Page 16: Weathering and Sedimentation

• Mechanical Weathering: Physical breakdown without altering chemical composition.

• Chemical Weathering: Alters minerals through chemical reactions, causing rock disintegration.

  • Examples: oxidation and hydrolysis.

• Sedimentation: Accumulation of sediment particles transported by natural forces.

Page 19: Geologic Hazards

• Natural Hazards:

  • Asteroid impacts (dinosaur extinction), floods (high mortality), and wind (property damage).

• Earthquakes: Sudden crustal movements along faults.

  • Epicenter is the initial point of movement.

Page 20: Earthquake Impact and Regions

• Poor construction increases death toll from earthquakes; reinforcement is now common.

• Most seismically active in the U.S. is the West Coast.

  • Largest recorded earthquake: New Madrid, Missouri.

Page 22: Volcanoes

• Major sources of Earth’s crust, also contribute to fertile soils through weathered volcanic material.

• Nuees Ardentes: Hot gas and ash clouds, extremely dangerous during eruptions.

• Eruptions can lead to mudslides and alter global climates through ash and gas emission.

Page 25: Landslides

• Definition: Movement of geological materials downslope due to gravity.

• Can vary in speed; roadwork and development can increase landslide execution and damage.