Earth Science: Plate Tectonics and Boundaries

• Earth science studies the Earth's physical constitution and atmosphere.
• Earth's age: 4.6 billion years.
• Seafloor spreading involves lithospheric plates pulling apart, allowing magma to rise at midocean ridges.
• Paleomagnetism records Earth's magnetic field polarity in rocks when they solidify.
• Plate tectonics theory: the lithosphere is divided into plates moving over the mantle due to convection.
• The largest plate is the Pacific Plate.
• Plate tectonics is driven by mantle convection, ridge push, and slab pull.
• Asthenosphere: a plastic layer in the upper mantle that deforms easily.

Plate Boundaries

• Convergent boundary: plates collide.
• Divergent boundary: plates move apart.
• Transform boundary: plates slide past each other.

Convergent Boundaries

• Plates may diverge, converge, or slide past each other.

Pacific Ring of Fire

• The Pacific Ring of Fire is known for high earthquake and volcano activity due to plate boundaries.
• About three-quarters of all active volcanoes are within the Pacific Rim.

Mantle Plumes and Convection

• Mantle plumes: columns of magma that rise to Earth's surface, related to hot spots.
• Convection: energy transfer through fluid movement due to density differences.

Pangaea and Continental Drift

• Pangaea: a supercontinent that began breaking apart millions of years ago.
• Alfred Wegener proposed the theory of continental drift.

Volcanoes

• Volcano: a mountain with a vent for eruption of lava, rock, gas, etc.
• Volcanic activity can both harm with lava flows, ash fall, and pyroclastic flow, but also benefit, creating fertile soils and geothermal energy.

Volcanic Terms

• Crater: a bowl-shaped depression.
• Conduit: a channel for conveying magma.
• Fissure: a long, narrow crack.
• Pyroclastics: fragmented rock and gas ejected during eruptions.
• Lahar: a volcanic mudflow.
• Parasitic cones: smaller cones on a larger volcano.
• Lava: molten magma on Earth's surface that cools and solidifies.

Intrusive vs. Extrusive Volcanism

• Intrusive volcanism: magma cools beneath the surface.
• Extrusive volcanism: magma erupts onto the surface.

Gases Released by Volcanoes

• Volcanoes release: 50-90% water vapor, 1-40% carbon dioxide, 2-35% sulfur gases.

Types of Volcanoes

• Shield volcano: A broad, gently sloping volcano formed by fluid lava flows.
• Cinder cone: A small, steep-sided volcanic hill formed by cinders and volcanic ejecta are around a vent.
• Lava dome: A steep-sided mound formed by viscous lava.
• Caldera: A large, bowl-shaped volcanic depression.

Phreatic Eruption

• Phreatic eruption: a steam-driven explosion from water heated by volcanic activity.

Earthquakes

• Earthquake: vibrations from abrupt crustal movement.
• Earthquake waves: vibrations that travel through Earth, carrying energy.
• Earthquake magnitude: the energy released during an earthquake.
• Tsunami: a long oceanic wave caused by a submarine earthquake, landslide, or eruption.
• Faulting: crust breaks and moves along a fracture.
• Four fault types: normal, reverse, thrust, strike-slip.
• Epicenter: location on the surface above the fault rupture.
• Seismograph: instrument measuring earthquake details.
• Mount Saint Helens is in Washington, about 96 miles south of Seattle, and 8,365 feet in elevation.

Earth Structure

• Crust: the outermost solid layer.
• Mantle: layer beneath the crust and surrounding the core.
• Core: the innermost part of Earth comprised of iron and nickel.

Uniformitarianism vs. Catastrophism

• Catastrophism: landscape formed by catastrophes.
• Uniformitarianism: Earth shaped by processes similar to today.

Law of Superposition

• Law of Superposition: oldest rock layers are at the bottom in undisturbed rock.

Relative Dating

• Relative dating: placing rocks and events in sequence.

Principles of Relative Dating

• Law of superposition: oldest rocks are on the bottom.
• Original horizontality: sediment is deposited horizontally.
• Cross-cutting relationships: younger feature cuts through an older one.

Fossils

• Petrified: cavities filled with precipitated mineral matter.
• Mold: shell is buried and dissolved.
• Cast: hollow mold space is filled with minerals.

Types of Fossil Preservation

• Carbonization: organic matter becomes carbon residue.
• Impression: replica of the fossil's surface.
• Preservation in amber: organism surrounded by hardened tree resin.
• Fossil succession: fossils in different strata represent different time periods.
• Index fossils: fossils associated with a specific geologic time.
• Radiometric dating: calculating rock ages using radioactive isotopes.

Geologic Time Scale

• Eon: largest unit on the geologic time scale, about 1 billion years.
• Era: major division on the geologic calendar.
• Paleontology is the study of fossils
• Fossils are traces or remains of prehistoric life preserved in rock

History of the Earth

• Photosynthesizing bacteria started releasing oxygen 3.5 billion years ago.
• Earth's atmosphere formed by outgassing (release of gases from the interior).
• Pangaea began to break apart 200 million years ago.

Phanerozoic Eon

• Phanerozoic history: 542 million years, which contains abundant fossil evidence.

Geologic Eras

• Paleozoic era: 540 to 248 million years ago, Pangaea assembled.
• Mesozoic era: 248 to 65 million years ago, age of the dinosaurs.
• Cenozoic era: 65 million years ago to present.

Time Periods

• Trilobites: Cambrian period.
• Permian period: mass extinction of marine and vertebrate organisms.
• Mesozoic: age of reptiles.
• Rock cycle: recycling of mineral material.

Geomorphology

• Geomorphology: the study of landforms.
• Types of Rocks: igneous, metamorphic, and sedimentary.
• Extrusive volcanism: volcanism occurring on Earth's surface.
• Intrusive volcanism: plutonic activity occurring below the surface.
• Igneous rocks are the most abundant rock type.
• Minerals are made of elements; rocks are made of minerals.
• Metallic Mineral Resources: Gold, silver, copper, mercury, lead, etc.
• Most sedimentary deposits are built up in horizontal layers called strata.

Minerals

• Mineral: a naturally formed solid inorganic substance with a crystal structure and specified chemical composition, composed of elements.
• Mineral characteristics-
• Ordered internal structure
• Definite chemical composition
• Element - Basic building block of minerals: Defined by number of protons:
• Atom - Smallest particles of matter: Have all the characteristics of an element

Physical Properties of Minerals

• Habit: common crystal shape.
• Luster: surface appearance.
• Color: recognizable feature.
• Streak: powdered form color.
• Hardness: resistance to scratching.
• Cleavage: splitting related to internal structure.
• Specific gravity: weight of a mineral.
• Fracture: random breakage pattern.
• Tenacity: resistance to deformation.
• Plutonic/Intrusive: formed deep underground from magma.
• Volcanic/Extrusive: formed on the surface from lava.

Mineral Resources

• Mineral resources: useful minerals that will be extracted.
• Ore deposits: metallic mineral concentrations mined at a profit.
• Economic factors influence resource profitability.
• Geomorphology: The study of the characteristics, origin, and development of landforms.