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113 Cards in this Set
- Front
- Back
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Major Components of Continents
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Shields, Stable platforms, Belts of folded mountains
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Internal layers of earth based on COMPOSITION
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Crust (silicates), mantle (silicates), core (iron)
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Internal layers of earth based on PHYSICAL PROPERTIES
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Lithosphere (rigid), Athenosphere (plastic- partially molten), Mesosphere (solid), Outer Core (liquid), Inner core (solid)
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Major processes
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Tectonism, volcanism, hydrological, eolian (wind), [impacts]
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Accretionary heat
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Heat caused by the collision of meteorites and asteroids that eventually formed Earth and other non-gaseous planets
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What kind of plate boundary is found at mid-ocean ridges?
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Divergent plate boundary
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What kind of plate boundary is associated with domes, flows, explosive and composite volcanoes (steeper volcanoes)?
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Convergent plate boundary
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Why does intraplate volcanism occur?
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Convection in the mantle causes plumes to rise and heat up the bottom of a plate, which creates molten rock that rises to the surface
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Strombolian Style
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The bubble rise rate is GREATER THAN the magma rise rate, which leads to SPATTER CONES (think of STROMBOLIAN SPATTER)
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Hawaiian Style (Shield Volcanoes)
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The magma rise rate is GREATER THAN the gas (bubble) rise rate, which means bubbles come out at the same time as the magma
Creates CINDER CONES |
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Dome Growth
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Viscous, gas-rich magma rises and builds up in layers to form a dome (not enough gas or pressure to have explosive events, usually). Forms a brittle lid on top, while the molten rock coming up fractures it and causes it to grow. Through these fractures the lava degasses.
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Plinian style
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A low viscosity gas-clast mixture rises, its pressure greatly exceeding atmospheric pressure. The exit velocity is high, and the surrounding atmosphere is sucked in and heated. The eruption produces a turbulent, buoyant cloud that rises very high. Occasionally, the cloud collapses to form destructive pyroclastic flows.
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Basaltic Flows: Two Types
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Aa flow and Pahoehoe flow
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Aa flow
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Slow. Rough surface because the surface cools as the interior stays molten, causing the crust to break and form angular fragments. Vesicles make the resulting rock light and porous.
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Pahoehoe flow
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More fluid. The crust is thin and glassy (much more smooth than Aa flow), and gets wrinkled into folds. Commonly forms a PRESSURE RIDGE (a central fracture through which gas and lava can escape).
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Columnar joints
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A system of polygonal cracks that can develop as a flow cools and contracts
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Lava tube
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When the sides and top cool and become solid and the fluid interior breaks through the crust and flows out.
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Fissures
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A series of fractures in the crust
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Spatter Cones
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Small conical mounds formed when rising lava is concentrated and erupts like a fountain, with bubbles rising faster than the magma.
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Flood basalts
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Volcanic deposits
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Tephra
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Volcanic ash and dust
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Volcanic bombs
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Larger fragments of cooled lava
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Cinder cone
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Larger particles of tephra accumulate close to the vent and form this
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Shield Volcano
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What may eventually form around a central vent or series of fissures where the extrusion of fluid basaltic lava dominates. It has a wide base and gentle slopes. (EX: Hawaiian volcanoes) Often have basaltic calderas. Underwater shield volcanoes will extrude pillow lava.
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Calderas
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Summit craters. Formed after the eruption/emptying of magma below, when the rock on top lowers or collapses into the available space.
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Pillow lava
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A flow composed of many sphere- or ellipse-shaped masses
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Kinds of Silicic Eruptions
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Lava domes, composite volcanoes/stratovolcanoes
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Ash flow
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The lateral flow of large masses of pumice and ash at a great velocity. When it comes to rest, the particles may fuse to form welded tuff.
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Ash-flow calderas
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Largest silicic volcanoes on Earth. Made of far-traveled sheets of tuff. Very low, very broad shields dominated by the central collapse structure (caldera).
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Are the rocks of the ocean floor older or younger than those of the continents?
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Younger! The mid-oceanic ridges extrudes new rock, which pushes the current rock. Plus, the rocks of the ocean floor haven't been deformed by compression.
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The Oceanic Ridge
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Most pronounced tectonic feature on Earth! It is a broad, fractured upwarped segment of crust that extends around nearly the ENTIRE GLOBE. A huge, crack-like RIFT VALLEY runs along most of the ridge.
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Trenches
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Lowest areas on Earth's surface. Associated with chains of active volcanoes, mountain belts, and zones of intense earthquake activity. Adjacent to island arcs or coastal mountain ranges.
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Islands/Seamounts
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Seamounts: submerged volcanoes
Both occur above mantle plumes and hot spots, not just at ridges |
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The Abyssal Floor
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Vast areas of broad, relatively smooth deep-ocean basins on both sides of the oceanic ridge. Includes both the ABYSSAL HILLS and the ABYSSAL PLAINS
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Abyssal Hills
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Relatively small ridges or hills that cover most of the seafloor (the MOST WIDESPREAD LANDFORMS ON EARTH!)
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Abyssal Plains
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Near continental margins. Land-derived sediment that completely covers the abyssal hills, forming a flat, smooth surface.
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Continental margins
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Zone of transition between a continent and an ocean basin
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Continental Shelf
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Submerged part of a continent-- geologically a part of the continent and not the ocean basin
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Continental slope
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Outer edge of the shelf slopes continuously into the deep-ocean basin. Marks the edge of the continental rock mass.
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Sources of energy of seismic waves
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Earthquakes, volcanic eruptions, impacts, explosions
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Earthquake effects
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Ground motion, landslides, tsunamis, soil liquefaction, uplift and subsidence of regions
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Earthquake Preparation: Seismic Risk Map
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Map of where past earthquakes have occurred, under the assumption that they will strike there in the future
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Types of Waves
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P-Waves, S-Waves, Surface waves
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P-Waves
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Primary Waves! They are COMPRESSIONAL, identical to sound waves passing through a liquid or gas.
They transmit energy by compressing and dilating the material through which they move. Usually have SMALLER AMPLITUDES THAN LATER WAVES. They are the FIRST TO ARRIVE AT SEISMOGRAPHS. They PASS THROUGH ANY SUBSTANCE/STATE. |
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S-Waves
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SECONDARY WAVES! They are SHEAR WAVES. Particles oscillate back and forth at right angles to the direction of wave travel. They are the SECOND TO ARRIVE, and they WILL NOT PASS THROUGH LIQUIDS.
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What do these waves provide evidence for?
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Where the S-Waves and P-Waves reach, compared to the origin of the earthquake, implies that there is a molten outer core and a solid inner core,
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Surface Waves
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Travel relatively slowly over Earth's surface, the last waves to arrive
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Seismic ray
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Line perpendicular to the wave front
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Shadow zone
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A large region on the opposite side of the planet from where the epicenter occurs where the resulting seismic waves are not detected.
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Seismic discontinuities
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Minor variations in seismic velocities with depth
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Convection
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Most important mechanism of heat transfer in Earth!
Convection in the iron core probably creates the magnetic field. In the mantle, it is responsible for mantle plumes (volcanism) and plate tectonics. |
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Orogeny
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Episode of mountain building
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Evidence for Continental Drift
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Fauna (African and S. American fauna similar in some areas), continuity, mountain ranges (e.g. India colliding with Asia), flood basalts, polar wandering, morphological fit, seafloor spreading (the mechanism!)
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Types of Plate Boundaries
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Divergent, Convergent, Transform
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Divergent Plate Boundaries
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Plates move apart (e.g. mid-oceanic ridges). Molten material from the mantle fills the void, some of which erupts on the seafloor and solidifies as a new part of the lithosphere. Causes shallow-focus earthquakes.
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Convergent Plate Boundaries
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Plates are consumed (SUBDUCTION). Intense compression, often leads to high-folded mountain belts. Causes many earthquakes and volcanic eruptions.
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Transform Plate Boundaries
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Shearing, where plates horizontally slide past one another. Shallow earthquakes common, volcanic eruptions uncommon. Most on seafloor. (Best-known example: San Andreas Fault systems in California). Marked by sharp linear landforms
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Strain
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Deformation of a rock's shape
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Shear
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Slippage of one bock past another
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Kinds of Stress
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Extensional stress (tension, rocks stretch and thin), Contractional stress (compression, rocks shortne and thicken), Lateral-slip stress (rocks slip past each other)
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Joints
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Tension fractures in rocks along which there is no horizontal or vertical displacement. Form at low pressure.
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Faults
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Fractures along which slippage or displacement has occurred. Normal faults, Thrust faults, Strike-slip faults
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Normal Faults
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Result of extension. Movement is mainly vertical. Commonly produces a cliff (scarp) at the surface.
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Thrust fault
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Result of horizontal compression. Movement in mainly horizontal. Can form an eroded scarp.
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Strike-slip faut
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Result of lateral slip. Straight valley or series of low ridges.
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Folds
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Warps in rock strata during ductile deformation
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Domes and basins
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Gentle warping, mainly sedimentary rocks at continental interiors
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Intrusive Rock
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Magma that solidifies below the surface
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Extrusive Rock
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Magma reaches the surface before cooling, flows over landscape as lava
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Volatiles
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materials that are readily vaporized to form gases at Earth surface conditions
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Textures of Igneous Rocks
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Glassy, Aphantic, Phaneritic, Porphyritic, Pyroclastic
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Glassy
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Very rapid cooling, no distinct grains visible, numerous vesicles
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Aphantic
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Rapid cooling, extremely fine grains, numerous vesicles
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Phaneritic
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Slow cooling, cooled far below the surface, grains visible to the naked eye
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Porphyritic
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Initial stage of slow cooling, followed by a period of more rapid cooling. Grains of two distinct sizes: PHENOCRYSTS (larger, well-formed crystals) and MATRIX/GROUNDMASS (smaller crystals)
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Pyroclastic
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Produced when explosive eruptions blow crystals and bits of molten magma into the air. When deposited, they are welded together.
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Types of Igneous Rock
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Granite, Diorite, Gabbro, Peridotite, Rhyolite, Andesite, BASALT, Komatiite, Tuff (rock resulting from the accumulation of pyroclastic fragments)
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Formation of Sedimentary Rocks
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Form from fragments of other rocks, chemical precipitates from water, and organic materials formed by biochemical processes (e.g. coral reefs).
Typically occur in strata/beds. HYDROLOGIC SYSTEM: Weathering of pre-existing rock, transportation of the material away from the original site, deposition of the eroded material in the sea or in some other sedimentary environment, compaction and cementation |
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Types of Sedimentary Rocks
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Clastic rocks, consisting of particles of gravel, sand, or mud (Subdivided according to grain size, large to small: Conglomerate, sandstone, mudrock)
Chemically precipitated rocks (Inorganic and Biochemical), such as Limestone |
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Sedimentary Rock Structures
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Stratification (reflect changes that occur during formation), Cross-bedding (strata inclined at an angle), Graded bedding (progressive decrease in grain size upward through a bed), Ripple marks (sediment deposited by wind or water), Mud cracks (sediment dried while being temporarily exposed to air)
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Primary Crust
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Heavily cratered, segregated crust, deeper unmodified mantle
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Secondary crust
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Partial melting of the primary crust, those materials create a new crust-> tectonic activity, seafloor spreading, volcanism, etc. are present (Mare terrain)
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Tertiary crust
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Metamorphism, melting, remelting, volcanism, reforming primary and secondary crust (e.g. Earth)
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Basic Provinces of the Moon
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Maria and Highlands/Terrae
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Lunar Maria
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The dark parts. Low albedo (what makes it dark), low elevation, smooth topography, few craters, few mountains, faults, lava flows, volcanoes, many ridges, sinuous.
Nearside! |
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Highlands
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High albedo, high elevations, rough topography, many craters, mountains near margins, faults, few ridges.
Farside! |
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Similarities between Earth and Moon
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2 major provinces with asymmetric distributions (Moon: Mare mostly on nearside, Earth: Continents mostly in northern hemisphere)
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Simple Craters
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Smaller than about 15 km in diam. Most common on any planetary body. Traditional bowl-shape.
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Complex craters
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>15km in diam. Typically have relatively flat floors, terraces on inner walls, and central uplift features.
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Impact Basins
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Much bigger. Extremely flat floors, can have multiple central uplift features that form rings within the basin. Many have been filled with basaltic lava since their formation.
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Formation of Craters
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Stage 1: Compression
Impact causes a shock wave that transfers the meteor's kinetic energy through the ground, expanding in a spherical pattern away from impact. The pressure is so high that the rock behaves like fluid for a short time. Stage 2: Excavation- After the shock wave, a reflecting rarefaction wave starts, allowing the rock to expand as the target returns to the same low pressure as the surroundings. Ejecta is blown from the impact site. The crater grows rapidly, attaining its final diameter before the ejecta hits the ground to form a ring or multiple rings. Stage 3: Modification- Central uplift is formed. Parts of the rock wall in the rim may slip, forming terraces. |
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Energy Partitioning
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The reservoir of energy from impact events is split:
25% Heating (melts the rocks, welds [agglutinates], metamorphism) 8% Comminution (fragmentation -> breccias) 20% Plastic viscous deformation (deforms impacted material) 50% Ejection of ejecta (Lateral transport, mixing, secondary cratering) <1% Seismic Waves (Massive Moonwide moonquake, landslides, degradation) |
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Layers of the Moon: Chemical Properties
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Crust, mantle, and core
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Layers of the Moon: Mechanical
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Lithosphere and Athenosphere
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Crust of the Moon
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Formed 4.6 billion years ago when the "magma ocean" that was the outer portion of the moon differentiated. The less-dense plagioclase feldspar rose to the top and cooled, creating the initial crust. This new crust then underwent a period of intense cratering.
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Regolith
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Lunar "soil". The surface regolith is impact regolith, which is mostly a fine dust after billions of years of impact events fracturing and uplifting rock, mixing it and creating a diverse regolith. Beneath that is the megaregolith, mainly composed of fractured bedrock from large impact events.
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Rayed Craters
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YOUNGER than the mare basalts. The rays and ejecta of the impact are superposed on essentially every feature in their path. EX: Copernicus Crater
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"Eratosthenian" Crater
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Dark ejecta blankets, no rays. More subdued secondary craters. OLDER than rayed craters, YOUNGER than basalts. EX: Eratosthes Crater
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Imbrium Basin
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Multiring basin made by an impact event (the largest of its kind on the Moon), now largely filled with lava flows. Important ejecta deposits include the Montes Apenninus and the Fra Mauro Formation.
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The Ancient Terrae
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Complex sequence of craters and ejecta found in the lunar highlands, formed during the Nectarian period. Large craters, closely spaced, modified by impact. The lavas that fill the craters are much younger.
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Oldest materials on the moon?
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Pre-Nectarian Rocks!
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Cratering
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Telling how old a terrain is by the number of craters it has. LIMIT: At some point, the number of carters stops telling age because new craters are just being made over old ones
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Radiometric Dating
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Most rocks contain elements that decay to other ones, which means we can tell how old they are (generally) by seeing how much has decayed
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Minerology
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Using special imaging devices to separate different parts of the topography, revealing the mineral composition and showing what parts are of the same types and the same time
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Evidence of Volcanism on the Moon
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Mare surfaces (basaltic lava), a few volcanic shields, flow margins formed by more viscous lava in the Mare Imbrium, sinuous rilles, smooth low domes, glass beads (spatter that cooled quickly)
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Lava flows/eruptions on the Moon vs Earth
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Eruption rate for mare lavas higher than any on Earth, lava more fluid than any on Earth, an eruption would cause a cloud of rising ash and tephra to spread and be deposited much farther away, can't really form cinder cones
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Sinuous rilles on the Moon
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Originates from a collapsed lava tube or from fault-troughs modified by flowing lava, imply high effusion rates
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Floor-fractured crater
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Theory of shallow intrusion: lava pushes up against the floor, inflates it and cracks it, moves laterally in the crater
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Ascent and Eruption of Mare Basalts
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1) Rock is melting 100s of kms under the surface
2) Rise until it encounters the crust, at a point of neutral density (more dense than the crust, less than the mantle) 3) More molten rock gathers at the underside of the crust 4) A crack (dike) forms due to stress and pressure 5) Some cracks make it to the surface, lava flows out |
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Major Lunar Rock Types
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Plutonic rocks, mare basalts, breccias
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Plutonic rocks
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Primarily anorthosites and gabbroic anorthosites, igneous origin, formed by the cooling of magma at depth
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Mare basalt
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Igneous rock, forms the mare plains, originated in the lunar mantle after the initial differentiation and cooling of the lunar interior. Contains plagiocase feldspar, pyroxene, olivine, and ilmenite
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Breccia
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Formed during impact events. Made up of other rock materials (typically has cataclastic texture due to fragmentation from impacts)
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