GEOL 101 Exam 1 Review

Chapter 1: The Universe and Earth

Big Bang (13, 15)

• The Big Bang Theory proposes that all matter and energy in the Universe started out as a single infinitesimally small point.

• The galaxy continues to expand.

• First element formed = Hydrogen

• Hydrogen fused to helium, initiating a star.

Stars, supernovas, and the formation of elements (18, 19)

• Stars have a finite amount of hydrogen.

• Hydrogen is their main fuel.

• When it runs out of hydrogen, it gets dark.

• When supermassive stars die, they explode in a supernova.

• Big Bang nucleosynthesis formed the lightest elements.

  • Hydrogen and Helium.

• Stella nucleosynthesis led to fusion of elements during the life cycle of a star.

  • Up to Iron (Fe)

• Elements with atomic numbers larger than 26 formed during supernovae nucleosynthesis (atomic number 27 to 92).

Nebular theory - formation of a solar system (22)

• Cosmic dust - a mass of hydrogen, helium, and other elements.

• Cosmic dust and gas begin clinging together due to electrical charges that act on them.

• They build a mass and collect more debris, forming a planet.

• When that happens, the mass causes the hole of the nebulous cloud to start rotating around and flatten out.

Mass of sun, composition of planets – refractory vs. volatile (24)

• 99.98% of all of the material that was once in the nebulous cloud is now held within the sun.

• A blast sent out lighter elements and pushed them to farther parts of the solar system.

• The heavier elements, refractory elements, came together to make up rocky bodies.

• Four terrestrial planets (Mercury, Venus, Earth, Mars) are smaller than the gas planets.

  • All condensed down under refractory materials.

Differentiation (28)

• When our planet began forming, denser material started to sink to our core.

• Heat caused the material to flow under gravity.

• Differentiation is the organization of the Earth into layers.

• Led to the formation of a core, a crust, and eventually continents.

• The light elements were driven from the interior to form an ocean and atmosphere.

• Denser elements = core

• Lighter elements = surface

• Differentiation created the magnetosphere, atmosphere, and our tectonic plates.

We are the stars (30)

• Dust particles and stony debris from supernovae coalesced to create the planetsimals that amassed together to form the Earth.

• Our planet and ourselves are made up of the elements of exploded stars.

Asthenosphere, lithosphere, and Earth’s layers (49, 50)

• Using sound waves, we can know what the interior of the Earth looks like.

• The interior is divided up in layers:

  • Crust - made out of lighter minerals

  • Upper mantle

  • Transition zone

  • Lower mantle

  • Outer core - liquid

  • Inner core - solid

• By volume, the most of our planet exists in the mantle.

• Lithosphere - the crust and upper mantle, both act rigid.

• Asthenosphere - the soft layer in the lower part of the mantle.

  • Where melting occurs.

• Our tectonic plates are comprised of the lithosphere.

• Below the tectonic plates is the asthenosphere.

• Tectonic plates are moving and recycling material and hydrating out the lighter materials.

• Continental crust - thicker, less dense.

• Oceanic crust - thinner, denser.

Compare compositions and density to Earth’s layers, and geothermal gradient (51)

• The mantle comprises most of the Earth’s mass.

• The outer core is liquid.

• The inner core is solid.

• The temperature and the pressure both increase as we go deeper within the Earth, toward its core.

Chapter 3: Minerals

Definition of a mineral – 5 criteria (4)

• Naturally occurring

• Formed by geologic processes

• Inorganic

• Crystalline solid

• Definite chemical composition

What qualifies as a mineral (10)

• Table salt

Crystal formation (12)

• Minerals are composed of 1 or more elements, the atoms are bound together by chemical bonds.

• A crystal is a single continuous piece of crystalline solid typically bounded by flat crystal faces.

  • Minerals are not always found as perfect, full crystals.

• Crystal faces grow naturally as the mineral forms and reflect atomic structure, growing in an orderly arrangement of atoms.

  • Example: prismatic

  • Its touching silicon and oxygen ions in a scaffolding way.

• The geometry of the atomic arrangement defines the crystal structure and the nature of chemical bonding determine the mineral properties.

• Lattice structures give us sets of properties for us to test minerals (clues on how to identify mineral).

Atomic bonding, polymorphs of Carbon (13)

• Covalent bonds in a mineral can determine strong the mineral is.

• Molecules help form a pattern in the structure of a mineral.

• The two polymorphs of carbon (diamond and graphite) are the hardest and softest minerals, a result of different types of chemical bonds.

• Color is not a good way to identify minerals, do not look at color first. Many minerals vary is color. Quartz can be any color, for example.

• Different minerals grow different crystal shapes.

• Crystal habit - is the ideal shape of the crystal.

Euhedral vs. anhedral crystals (19)

• Euhedral crystals - Minerals with well-formed crystal faces.

• Anhedral crystals - Minerals without well-formed crystal faces.

Different settings where minerals form (20-24)

• Solidification - occurs when molten rock, such as lava or magma, cools and different minerals grow in succession.

  • Can happen below the earth - intrusive.

  • Can happen above the Earth’s surface - extrusive.

  • Certain minerals crystallize at certain temperatures as the magma is cooling down.

• Precipitation - occurs from volcanic gas, deep sea, hydrothermal vents, or element-rich gas. Occurs when water in a salty desert undergoes evaporation.

• Bio-mineralization - Refers to the production of minerals by organisms. Reef organisms, extra ions from water to make shells.

• Diffusion - Metamorphic process, atoms migrate through the crystal and new minerals grow inside the rock, happens slowly.

• 3 ways in which minerals can be destroyed:

  • Water

  • Erosion

  • Heat/melting

Physical properties - represent crystal structure and chemical composition (28-37)

• What to look at when identifying minerals:

  • Color - a diagnostic of some minerals (turquoise) but a poor indicator for others (quartz).

  • Hardness - The scratching resistance of a mineral, which is directly linked to chemical bond strength.

  • Streak - The color of a mineral when it is powered (rubbing it on an unglazed porcelain plate).

  • Luster - Luster refers to the way that a mineral surface scatters light.

  • Cleavage - The tendency for a mineral to breakalong lattice planes with weaker atomic bonds.

  • Fracture tendency - Minerals fracture when they break through the lattice planes instead of along them.

  • Reaction to acid

  • Crystal habit

Silicate minerals are the most common rock forming mineral group on Earth (45-48)

• Silicate minerals are by far the most dominant substances comprising Earth’s crust (90%) and mantle (>99%).

• Silicon and oxygen account for more than 74% of crustal mineral mass.

• Silica tetrahedron

• Isolated tetrahedron

• Single chain

• Double chain

• Sheet

• Framework

Minerals are important! (60)

• Minerals make up many items we use on a daily basis (phones, counters, wires, construction equipment).

Chapter 4: Igneous Rocks

Cemented vs. crystalline rocks (4, 5)

• Crystalline rocks are held together by interlocking crystals.

• Cement - like glue, it is deposited between little tiny pore spaces between crystals.

Intrusive vs. extrusive, and connect that to igneous rock texture (15)

• Lava is found on Earth’s surface.

• Magma is found below the surface.

• The extrusive realm is above ground.

• The intrusive realm is below ground.

  • Results in crystals

How melting occurs – decompression, flux, heat transfer – and the settings where these occur (22-26, 28)

• Decompression melting

  • Pressures decreases but temperature remains constant, creating a melt.

  • Changing pressure (relieving pressure), not temperature.

  • Where: Geologic environments where decompression melting occurs:

    • Decompression melting occurs at mantle plumes, continental rifts, and divergent-plate boundaries.

  • Rift zone - where Earth is being pulled a part.

  • Decompression melting happens at mid-ocean ridges.

  • Black rocks from decompression melting spill on surface (basalt).

• Add volatiles (flux)

  • Volatiles help break chemical bonds, creating a melt (molten rock).

  • Volatiles are gaseous components of magma that can vaporize at surface pressures (can easily vaporize).

  • Takes place at subduction zone.

  • Volatiles such as H₂O and CO₂ are driven from the oceanic crust into the asthenosphere, creating a melt above the sub-ducting plate.

  • Flux happens along subduction zones

• Heat transfer (conduction)

  • Heat from magma melts adjacent rocks, more melting.

  • Rocks surrounding magma chambers can be melted through heat-transfer.

  • Sharing heat.

Silica content composition (mafic → felsic) (32, 34)

Partial melting and resulting composition (36)

• Based on base rock/source rock.

• The source rock dictates the initial melt composition.

• Partial melting of rocks makes the melt silica-enriched because felsic minerals melt first.

  • Low temperature rocks.

• Partial melting - when heat is introduced to a solid rock (source rock).

Viscosity of different types of lavas (42, 43)

• The resistance to flow, or viscosity of a liquid affects the speed at which the liquid moves.

• Viscous - having a thick, sticky consistency between solid and liquid; having a high viscosity.

• Not all molten rock has the same viscosity. The viscosity of molten rock depends primarily on its:

  • Temperature - a lower temp melt is more viscous than a higher temp melt.

  • Volatile content - a wet melt containing more volatiles is more viscous than a dry (volatile free) melt.

  • Silica content - a felsic melt is more viscous than a mafic melt, because relatively more silicon-oxygen tetrahedra occur in a felsic melt.

Bowen’s reaction series (49)

• Rocks formed from the top of the series are felsic.

• Rocks formed from minerals at the bottom of the series are mafic.

• From top to bottom (low to high temperature):

  • Felsic (high silica content)

  • Intermediate

  • Mafic

  • Ultramafic (low silica content)

Intrusive igneous bodies (dikes, sills, plutons) (58, 59)

• Dikes run vertically and cut across rock layers.

• Sills run horizontally and are parallel to rock layers.

• Dikes can spread rocks apart sideways, sills push rocks up and can change the relief.

• Plutons are blob-shaped intrusions that solidify from magma chambers.

Igneous rock texture (phaneritic, aphanitic) (67-69)

• Aphanitic - extrusive, formed outside, fine-grained

• Phaneritic - intrusive, formed inside, coarse-grained

Chapter 5: Volcanoes

Olympus mons on Mars (6)

• Largest volcano in our solar system.

Types of volcanoes (shield, cinder cone, stratovolcano, supervolcano, hot spot, mid-ocean ridge) and examples of each (8-13)

• Shield

  • Broad, gentle domes whose shape resembles a soldier's shield lying on the ground.

  • Form when the products of eruption have low viscosity and can't build into a mound at the vent.

  • Constructed by lateral flow of low viscosity, basaltic lava (mafic)

  • Flow easily and spread out in thin sheets over large areas

  • Example: Kilauea (Hawaii)

• Cinder cone

  • Cone-shaped piles of ejected basaltic lapilli-sized fragments that have built up at the angle of repose around the vent.

  • Steep slopes, maximum slope that the loose fragments can sustain before sliding down, smallest type of volcano.

• Stratovolcano

  • Composite volcanoes

  • Constructed from alternating layers of high viscosity, andesitic or rhyolitic lava (felsic), tephra, ash, and debris.

  • Largest, most explosive, viscous, steep slopes

  • Example: Mt. St. Helens, Mt. Fuji, Mt. Rainier, Mt. Vesuvius

• Supervolcano

• Hot spot

  • Oceanic hot spot volcano forms on oceanic lithosphere, basaltic magma erupts at the surface on the seafloor.

  • Continental hot spots and rifts produce both effusive and explosive eruptions.

• Mid-ocean ridge

  • Develop along fissures parallel to the ridge axis.

  • Erupt basalt which cools quickly underwater and forms pillow lava mounds.

  • Water heats up as it circulates through the crust near the magma chamber bursts out of hydrothermal vents along the mounds.

Calderas (19)

• An enormous volcanic depression, much larger than a crater.

• Forms when a magma chamber empties and the volcano collapses into the evacuated space.

• A large circular depression with steep walls and a fairly flat floor, formed after an eruption as the center of the volcano collapses into the drained magma chamber below.

• Example: Crater lake, Oregon and Yellowstone National Park.

Viscosity of magma/lava, effusive vs. explosive (23)

• Effusive eruption

  • Low viscosity lava spills or fountains steadily from a vent or fissure.

  • Mafic.

  • Shield, fissures, mid-ocean ridges.

  • Basaltic lava flows, low silica, moves fast.

• Explosive eruption

  • Pyroclastic debris blasts forcefully into the air.

  • Andesitic lava flows, viscous, not fast, mounds around vent.

  • Rhyolitic lava flows, most viscous, slowest (rarely flows), lava plugs vent as lava dome.

  • Explosions due to pressure.

Types of effusive basaltic lava (pahoehoe, A’a’) (25, 26)

• Pahoehoe - basalt lava with ropy texture. Forms when extremely hot basalt cools, rolled ridges and furrows result in the cooling process because the lava is still flowing.

• A’a’ - Basalt lava that solidifies with a jagged, sharp, angular texture. Forms from Pahoehoe.

Columnar jointing (28)

• Columnar jointing - a type of fracturing that yields roughly hexagonal columns of basalt; columnar joints form when a dike, sill, or lava flow cools.

Pillow basalt (29)

• Pillow basalt - when lava cools quickly in water, submarine basaltic lava travels short distances before freezing, which produces a glass-encrusted blob. Glass rind of pillow momentarily stops the flow, then pressure from the lava squeezing into the pillow breaks the rind and a new blob squirts out. Process repeats.

31 – Explosive volcanic textures (pyroclastic, tuff, obsidian – volcanic glass)

• Pyroclastic - mix of rock fragments, pumice, and volcanic ash.

• Tuff - volcanic ash and fragmented pumice, when debris accumulates and cements together, glass shards.

• Tephra - volcanic deposits of pyroclastic debris of any size.

• Obsidian - volcanic glass.

32 – Explosive volcanic features - lahar, debris flow, ash fall, pyroclastic flow

• Lahar - A muddy, rapidly flowing slurry caused by ash-rich debris becoming very wet.

• Debris flow - wetted debris that moves downhill. Moves like wet concrete.

• Pyroclastic flow - an avalanche of hot ash, gas, and debris. Pompeii.

38-43 – Volcanism at tectonic plate boundaries & where mafic, felsic, intermediate rocks occur (basalt, andesite, rhyolite)

• Mid-ocean ridges

  • MOR-generated oceanic crust covers 70% of earth - largest magmatic systems from decompression melting of mantle rock.

  • Low silica

  • Low heat

  • Mafic lava (fast)

  • Low volatiles

  • Low viscosity

  • Effusive

  • Basalt rocks

• Convergent boundaries (arc)

  • Most stratovolcanoes form at convergent boundaries, from flux melting in the lithosphere.

  • High silica

  • Low heat

  • Felsic lava (slow)

  • High volatiles

  • High viscosity

  • Explosive

  • Andesite and Rhyolite

• Continental rift zones

  • Caused by fractional crystallization and assimilation or heat transfer

  • melting continental crust

  • High silica

  • High and low heat (when it sits in a chamber to cool longer)

  • Felsic lava (slow)

  • Low volatiles

  • Low viscosity

  • Effusive

  • Basalt

• Hot spots

  • Decompression melting in asthenosphere and lithosphere creates large volumes of magma

  • High and low heat

  • High volatiles

  • High viscosity

  • Explosive

  • Basalt

44, 45 - Famous volcanoes – Hawaii, Iceland, Mount St. Helens, Yellowstone

• Iceland - mantle plume hot spot coinciding with a mid-ocean ridge.

• Yellowstone - Mantle plumes that cut through continental crust create large volumes of felsic magma.