SIO 10 Midterm Review Notes

1.2 What Is the Structure of the Universe?

• Two competing views of the Universe:

  • Geocentric (~150 C.E.): All heavenly bodies circle around Earth, which is at the center of the Universe.

  • Heliocentric (1500 years later!): Earth, planets, stars, etc. circle around the sun.

  • To explain retrograde motion, astronomers had the planets move in small circles as they orbited Earth.

• The heliocentric (Sun-centered) view of the universe is a better model than the geocentric view, but our Sun is not the center of anything beyond our solar system.

1.2 What Is the Structure of the Universe? Definitions:

• Star: immense sphere of incandescent gas, mostly Hydrogen ($H$) with some Helium ($He$), held together by gravity.

• Almost all stars are orbited by planets that have coalesced from a disk-shaped “nebula” of gas and dust.

• Galaxy: immense groupings of stars (100s of billions).

• Universe: immense grouping of galaxies (100s of billions).

1.4 Where do the elements (different kind of atoms) come from?

• STEP 1: The “Big Bang” (hypothesis for earliest history of universe).

  • Formation of Hydrogen ($H$) and Helium ($He$) –– the simplest elements.

• STEP 2: Gravity causes collapse of H/He gas clouds into first stars.

  • Nuclear fusion in stars burns light elements to produce energy and heavier elements, up to Iron ($Fe$).

• STEP 3: When H/He supplies get low, there are different paths a star can take, including several that involve the explosion of the star in a “supernova.”

  • Supernova synthesize heavier elements.

  • Most elements heavier than oxygen made this way.

1.4 Where do the elements (different kind of atoms) come from?

• Top 10 most common elements.

  • Created in the Big Bang.

  • Created during stellar fusion (stars).

  • Created in supernova.

1.5 Formation of our Solar System

• Nebular theory of solar system formation.

• Planetesimals grow by continuous collisions.

• The interior heats up, and gravity pulls the material into a sphere, forming planets and moons.

1.2 Our Solar System

• We’re relatively close to the Sun! It’s warm, but not too warm.

• We’re somewhat small! (Gravity is strong, but not crushing).

Chapter 2: Earth's composition and structure

2.2 Journey Through the Solar System

• The planets, in order of distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

• Note the similar sizes of the “rock” component of the planets.

• Planets in a star’s “habitable zone” are at the right temperature to host liquid water at their surface: not too hot to boil the water away, not too hot that all the water freezes.

2.2 Journey Through the Solar System

• The terrestrial (rocky) planets: Mercury, Venus, Earth, Mars.

  • Mercury:

    • Atmosphere: None

    • Temperature: -180~430ºC

    • Surface Water: None

  • Venus:

    • Atmosphere: 50x denser than Earth’s

    • Temperature: 470ºC (melts lead)

    • Surface Water: None

  • Earth:

    • Atmosphere: Earthlike

    • Temperature: Cool/Warm

    • Surface Water: Liquid

  • Mars:

    • Atmosphere: Thin

    • Temperature: Cold

    • Surface Water: Ice

  • Habitable Zone (liquid water can/could exist on planet surface).

2.2 Journey Through the Solar System

• Mars Mudstones studied by the Curiosity Rover are evidence of liquid water on Mars at some point in the past.

2.4 ~ 2.5 Earth’s interior composition and structure

• Earth is almost entirely comprised of just four elements:

  • 30% Oxygen ($O$)

  • 35% Iron ($Fe$)

  • 15% Silicon ($Si$)

  • 13% Magnesium ($Mg$)

• Earth differentiated over time into a rocky (silicate) mantle and a nickel-iron core. Why?

  • lighter stuff → mantle

  • heavier stuff → core

• Iron sank into the core.

• The mantle is made of rocks consisting of a silicate (e.g., $SiO_4^{4-}$) in some combination with Magnesium ($Mg^{2+}$) and, to a much lessor extent, other elements.

• Iron is a metal that is denser than mantle rock.

• Iron migrated (sank) toward the center of the early Earth because it experienced a higher gravitational force than the rocks around it.

2.4 ~ 2.5 Earth’s interior composition and structure

• Layers of Earth

  • Crust: rocky, cool

  • Mantle: rocky, hot

  • Outer core: iron, hotter

  • Inner core: iron, really hot

• Geotherm: actual temperature inside Earth

2.4 ~ 2.5 Earth’s interior composition and structure

• Layers of Earth

  • Crust: rocky, cool, solid

  • Mantle: rocky, hot, solid but able to flow

  • Outer core: iron, hotter, liquid

  • Inner core: iron, really hot, solid

• In the outer core, the temperature (geotherm) is slightly higher than iron’s melting point (solidus), which is why the outer core is liquid.

2.4 ~ 2.5 Earth’s interior composition and structure

• Layers of Earth.

  • Circulation of liquid iron in the outer core is the source of Earth’s magnetic field.

  • Crust: rocky, cool, solid

  • Mantle: rocky, hot, solid but able to flow

  • Outer core: iron, hotter, liquid

  • Inner core: iron, really hot, solid

2.4 ~ 2.5 Earth’s interior composition and structure

• How do we know these properties of Earth’s interior when we can’t sample them directly?

  • rocks → Composition of actual Earth crust and mantle

  • asteroids → Composition of material that coalesced into Earth

  • lab experiments → properties and type of rocks that form at depth

  • seismic waves → temperature/density/phase of Earth material

  • pull of gravity → mass and density of overall Earth (requires a high-density iron core)

• Crust: rocky, cool, solid

• Mantle: rocky, hot, solid but able to flow

• Outer core: iron, hotter, liquid

• Inner core: iron, really hot, solid

2.5 What are Earth’s Layers Made of?

• Crust / Mantle / Core: defined by compositional differences

  • Crustal material: Oxygen, Silicon, Aluminum

  • Mantle material: Oxygen, Silicon, Magnesium

  • Core material: Iron

2.5 What are Earth’s Layers Made of?

• The crust consists of a slightly different mix of elements than the mantle.

• It is divided into two types: Oceanic and Continental.

  • Continental crust (light and thick)

  • Oceanic crust (dense and thin)

2.5 What are Earth’s Layers Made of?

• The crust is also the topmost part of the lithosphere.

• The lithosphere is a cool and rigid layer that reaches down into the mantle.

  • Lithosphere = rigid crust and mantle

  • Asthenosphere = weak mantle (Greek asthenos = weak/soft)

2.5 What are Earth’s Layers Made of?

• Moho boundary is due to composition differences between crust and mantle.

• Lithosphere/Asthenosphere boundary is due to rocks becoming weaker as temperature increases with depth.

• Transition zone boundaries are due to the formation of new types of rocks under increasing pressure & temperature within the mantle.

2.3 Basic Characteristics of the Earth

• Earth topography (browns & greens) and bathymetry (blues).

  • continents + continental shelves

  • ocean floors

Chapter 3: Continental drift

3.2 Wegener’s Evidence for Continental Drift

• In 1912, a German climate scientist named Alfred Wegener presented a new idea for how Earth’s surface evolved over time.

• He called it “Kontinentalverschiebung” = “Continental” + “Shift” (or “Drift”).

• His idea was that the continents as we know them moved into their present locations slowly over time and that they had started out as a single huge landmass called “Pangea” (or “Pangaea”).

• Africa and South America shapes fit, same fossils, rocks similar

3.2 Wegener’s Evidence for Continental Drift

• Fit of the continents.

• Locations of past glaciations.

• Distribution of climatic belts.

• Distribution of fossils.

• Matching geological units.

• Continental drift is a great hypothesis for explaining a diverse set of observations, but it lacked a plausible mechanism by which it could occur… hence the pushback against the theory by other scientists.

3.3 The Discovery of Seafloor Spreading

• Breakthrough results:

  • Discovery of ridges and trenches.

  • Sediment thickness increases away from ridges.

  • Earthquakes are located at ridges and trenches.

  • Heat flow from the mantle is concentrated at ridges.

• Breakthrough technologies:

  • SONAR, to map seafloor bathymetry

  • Seismic profiling

  • Continuously operating seismometers

  • Seafloor drilling

3.3 The Discovery of Seafloor Spreading

• Explains why we see ridges and trenches.

• Explains increasing sediment thickness away from ridges.

• Explains why seismicity is located at ridges and trenches.

• Explains observations of high crustal heat flow at ridges.

• Putting it all together (Harry Hess’s theory of seafloor spreading):

  • Mid-oceanic ridges are where hot magma rises and forms new crust, pushing the sides of the ridge apart. Shallow ridge earthquakes are due to rising magma breaking the crust.

  • Young oceanic crust ages as it moves away from the ridges, accumulating sediment, and cooling and sinking as it becomes more dense.

  • At the deep-ocean trenches, oceanic crust is ”subducted” or recycled back into the mantle, causing deep earthquakes.

3.4 Marine Magnetic Anomalies and Seafloor Spreading

• How Earth’s magnetic field is generated, according to Marshak: a nice orderly spiraling of liquid iron in the outer core.

• This is too structured to produce magnetic field reversals.

• A more realistic picture is given by simulations of liquid iron flow in Earth’s outer core.

3.4 Marine Magnetic Anomalies and Seafloor Spreading

• Earth’s magnetic field changes polarity regularly.

  • Sometimes Earth’s magnetic “North pole” is in the Antarctic. This is “reversed” polarity.

  • Sometimes Earth’s magnetic “North pole” is in the Arctic. This is “normal” polarity. (like now)

3.4 Marine Magnetic Anomalies and Seafloor Spreading

• Earth’s magnetic field changes polarity regularly.

• Ocean crust is magnetized with the polarity of Earth's field when it formed, then moves away as new crust is formed behind it.

• Liquid magma carries magnetized particles, which are free to move and align with Earth’s magnetic field.

• When magma solidifies, those magnetized particles freeze and preserve the orientation of the magnetic field: normal (black) and reversed (light purple).

3.4 Marine Magnetic Anomalies and Seafloor Spreading

• Earth’s magnetic field changes polarity regularly.

• Ocean crust is magnetized with the polarity of Earth's field when it formed, then moves away as new crust is formed behind it.

• We can map the resulting “marine magnetic anomalies” from ships.

3.4 Marine Magnetic Anomalies and Seafloor Spreading

• Marine Magnetic Anomaly Example: off Pacific Northwest Coast of USA

• Pattern of normal (colors) and reversed (white) polarity, extending outward from mid-ocean ridge (or spreading center) is clear evidence for creation and motion of new oceanic crust.

Chapter 4: Plate tectonics

4.2 The Concept of a Lithospheric Plate + Identifying P(whitlate Boundaries

• Continental crust is lighter and thicker.

• Oceanic crust is denser and thinner.

• Asthenospheric mantle slowly flows and moves out of the way of rigid lithospheric mantle.

4.2 The Concept of a Lithospheric Plate + Identifying Plate Boundaries

• Definition: A tectonic plate is a portion of Earth’s lithosphere (rigid crust + rigid layer of upper mantle) that moves as a single unit relative to other plates.

• Convergent (coming together).

• Trench; Collision

• Divergent (moving apart).

• Transform (sliding parallel).

4.2 The Concept of a Lithospheric Plate + Identifying Plate Boundaries

• Global Seismicity (Earthquakes) is concentrated at plate boundaries.

• Why? There must be a lot of stress on the (brittle) lithosphere at plate boundaries.

• Next, let’s find out how what is happening at those boundaries.

4.2 The Concept of a Lithospheric Plate + Identifying Plate Boundaries

• Divergent Boundary: plate motion moving apart.

• Convergent Boundary: plate motion coming together.

• Transform Boundary: plate motion sliding parallel.

4.2 The Concept of a Lithospheric Plate + Identifying Plate Boundaries

• Divergent Boundary (mid-ocean-ridge or spreading center; rift).

• Lithosphere.

• Asthenosphere.

• Mid-ocean ridge.

• Transform fault.

• Convergent Boundary (Subduction Zone).

• Overriding plate.

• Volcanic arc.

• Trench.

• Downgoing plate.

4.3 Divergent Boundaries and Seafloor Spreading

• Divergent Boundaries

  • Magma solidifies into new oceanic crust.

• Mantle material rises slowly (cm/year) at a mid-ocean ridge.

• A small fraction melts and turns into fast-flowing magma, which rises further and eventually reaches the seafloor.

• The gradual (cm/year) movement of oceanic crust away from the mid-ocean ridge is what is referred to as “seafloor spreading.”

• More magma makes its way to the surface as the sides of the mid-ocean ridge move apart. (It’s not entirely clear what causes what!)

• Earthquakes at mid-ocean ridges occur as new crust moves away from the ridge, cools, and becomes brittle.

• It takes a while for the stresses inside the crust to dissipate (mostly in the form of small- to-moderate earthquakes).

4.3 Divergent Boundaries (Mid-ocean Ridges, Spreading Centers)

• Details of a mid-ocean ridge spreading center.

• New pillow lava.

• Pillows.

• Dikes.

• Gabbro.

• Sediment.

• Mid-ocean ridge axis.

• Fault scarp.

• Median valley.

• Pillow basalt.

• Faults.

• Magma.

• Gabbro.

• Crystal mush.

• Lithospheric mantle.

• Asthenosphere.

• Dikes.

• Zone of partial melting.

4.3 Divergent Boundaries (Mid-ocean Ridges, Spreading Centers)

• Seafloor spreading occurs at different rates, depending on location, up to 15 cm/yr.

4.3 Divergent Boundaries (Mid-ocean Ridges, Spreading Centers)

• Question: Which ocean basin is growing the fastest?

• Pacific: 1.7 cm/yr

4.3 Divergent Boundaries (Mid-ocean Ridges, Spreading Centers)

• In Oceans: Juan de Fuca Ridge (offshore Pacific NW)

• New pillow lava.

4.3 Divergent Boundaries (Mid-ocean Ridges, Spreading Centers)

• Sometimes spreading centers are located on land.

4.3 Divergent Boundaries (Mid-ocean Ridges, Spreading Centers)

• On Land: Afar rift, Ethiopia (East African Rift)

• New pillow lava.

4.2 The Concept of a Lithospheric Plate + Identifying Plate Boundaries

• Convergent Boundary (Subduction Zone)

4.4 Convergent Plate Boundaries

• Japan (4 intersecting plates, 3 trenches, 1 collisional boundary).

4.4 Convergent Boundaries (Subduction Zones)

• Convergent Boundary (in this case: a Subduction Zone or Trench)

• Red dots are earthquakes occurring where parts of the crust are moving past each other.

• Yellow box shows area with potential for VERY large earthquakes (sediments from oceanic plate).

4.4 Convergent Plate Boundaries

• Deepest earthquakes.

• Sinking lithosphere may go to the core-mantle boundary.

• Wadati-Benioff zone

4.2 The Concept of a Lithospheric Plate + Identifying Plate Boundaries

• Collisional mountain belt. Detached, sinking oceanic lithosphere

4.2 Convergent Boundary (Collision Zone)

• Iran Plate

• Eurasian Plate

• India-Asia collision Zone

4.2 Convergent Boundary (Collision Zone)

• Himayan Front and Tibetan Plateau (a continental collision zone).

  • Himalayan Front

  • Tibetan Plateau

  • Sagarmatha / Mount Everest

4.5 Transform Plate Boundary

• Transform Boundary

4.5 Transform Plate Boundary

• What a Geologist Sees

• Transform boundaries (orange) are links between mid-ocean ridge segments (red)

4.5 Transform Plate Boundary

• The San Andreas Fault is a transform boundary between the North American and Pacific plates…that links spreading centers north of San Francisco and south of the Salton Sea.

4.5 Transform Plate Boundary

• The Big Bend restricts motion on the San Andreas Fault… perhaps encouraging a new transform fault inland

• High strain (surface deformation) colored red/orange

• New plate boundary forming?

4.8 Convection

• Heating at the bottom of a fluid layer (e.g., water, air, mantle) causes molecules to vibrate faster… which means they take up more space… and thus become less dense.

• Less dense (warmer) material rises, more dense (cooler) material sinks to take its place.

• That’s convection!

4.8 Mantle Convection

• Old idea: Convection drives large scale mantle flow. Plates move with the mantle. Not wrong, but too sVimplistic.

4.8 Mantle Convection

• Forces contributing to tectonic plate motion:

  • (ridge-push, pushing the plates apart)

  • (mantle-drag, dragging the plate from below)

  • (slab-pull, pulling the plate down behind it)

4.7 Hot Spots

• Volcanic islands in the Hawaiian chain are the result of magma erupting above a mantle plume (a “hot spot”)

• Seamounts (joined by colored lines) are volcanic islands that have eroded beneath the ocean over millions of years.

• They show where a tectonic plate has moved over a fixed hot spot location.

• Big change in direction 47 million years ago

4.7 Hot Spots

• Ages of the Hawaiian islands progress from young to old

• Current orientation of islands aligns with the orientation of seamounts to the west.

4.7 Hot Spots

• Recent Kilauea eruptions are occurring in the youngest area of the Big Island

• Lava flow ages on the BigH

• Continuous GPS (Global Positioning System) stations track current crustal motion

• Example locations: Nepal, Greenland, La Jolla

4.8 Moving plates

• With a few 1000s of GPS stations (red arrows), we can see details of crustal motion.. which suggest that tectonic plates are not entirely rigid, but can deform internally

• New plate boundary?

• Plate boundary

• Plate rotation

• Yellowstone Hot Spot

4.8 Moving plates

• Each arrow in this figure shows the motion of the crust (recorded by a GPS station).

• Lithosphere in the collision zone is being slowly, but violently, deformed. This generates earthquakes.

• Plate rotation and deformation

4.8 Moving plates

• Afar, Iceland, Caroline, Lord Howe, Bowie, Azores, St. Helena, Tristan de Cunha, Cobb, Yellowstone, Comorer, Crozet, Hawaiian, Bermuda, Ninetyeast, Kerguelen, Emperor, Great Canary, Trinidade, Marion, S. East Tasman, Hawaii, Camerron, Australia, Socorro, Cape Verde, Bouvet, Galapagos, Belleny, Samoa, Meteor
  Pitcairn, Louisville, Easter, Juan Fernandez, Macdonald
  (cm/yr)

4.8 Moving plates

• Putting it all together

Interlude A: Rocks

• Rock: a naturally occurring solid that typically consists of one or more minerals arranged in an irregular pattern

• Mineral: a naturally occurring solid that has a crystalline structure (where atoms are well ordered, like stacked oranges) and a consistent elemental composition

• Element: a species of atom with a fixed number of protons in the nucleus (e.g., Hydrogen is an element with 1 proton, Carbon is an element with 6 protons)

• Graphite is also a mineral made entirely of carbon

• Diamond: a form of crystalline carbon found naturally in kimberlite, a volcanic rock formed deep in Earth’s crust.

• Diamond is a mineral made entirely of carbon.

• Crystal structure is tetrahedral

• Crystal structure is hexagonal

• Kimberlite is a rock made of various minerals that are found deep in Earth’s crust.

• Kimberlite Locations South Africa with Kimberlite Pipes which are the remnants of old volcanic eruptions that once brought diamonds up from where they form in the upper mantle (100 km depths)

• 93% of the whole Earth is comprised of just 4 elements:

• 95% of Earth’s crust is comprised of just 5 elements:

• 93% of the whole Earth is comprised of just 4 elements:

• 95% of Earth’s crust is comprised of just 5 elements:

• Most rocks are made of just a few elements (ingredients) that were subject to heat and pressure (cooking) in various combinations (recipes) within the Earth. Even rocks with nearly identical elemental compositions can vary widely in density, hardness, brittleness, viscosity, etc.

• Metamorphic

• Sedimentary

• Igneous

Chapter 6: Magma & Igneous Rock

Chapter 6. Igneous Rock

• Igneous Rock: rock made by the freezing of a melt

• “Ignite” like fire

• Igneous solidification molten rock

Chapter 6. Igneous Rock

• Typical locations of igneous rock formation

• Example locations: Mid ocean ridge, Subducting plate, Volcanic arc, Kauai, Oahu, Molokai, Maui, Hawaii, Niihau, Plate motion, Lanai, Kahoolawe

• Rising magma, Hot spot, Rising plume of hot mantle rock.

• Volatiles released from the crust overlying asthenosphere melts.

Chapter 6. Igneous Rock

• Pillow lava is igneous rock that we can see being created on the seafloor at a mid-ocean ridge

Chapter 6. Igneous Rock

• Example locations: Kauai, Oahu, Molokai, Maui, Hawaii, Niihau, Plate motion, Lanai, Kahoolawe rising magma, rising plume - Kilauea eruption

Chapter 6.2, 6.7 Igneous Rock Origins

• Hotter magma is “mafic”: low silica

• Cooler magma is “felsic”: high silica

6.3, 6.4 Igneous rock characteristics

• Shield Volcano: formed from hotter lava that flows quickly (less viscous)

• Mauna Kea.

6.3, 6.4 Igneous rock characteristics

• Stratovolcano : formed from cooler lava that flows slowly (more viscous)

• Mt. Fuji (or Fuji-san)

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Extrusive realm

• Intrusive realm

• Ash cloud, ash fall, ash flow, lava flow, volcanic debris flow, magma chamber

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Here are some extrusive igneous rocks produced from mafic lava low-viscosity, easy-flowing

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Basaltic Lava Flow: A’a (faster/cooler) Pahoehoe (slower/hotter)

• Same lava composition, but different rock appearance due to temperature and flow speed (slower/hotter = Pahoehoe, faster/cooler = A’a)

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Thick mafic lava flow (very slow cooling): Basalt Columns

• Devil's Postpile National Monument (near Mammoth Mountain, CA)

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Here are some extrusive igneous rocks produced from felsic lava high-viscosity, slow-flowing, explosively erupting

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Felsic Lava Explosion: Lava Bombs

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Felsic Lava Explosion: Pumice

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Felsic Lava Explosion: Pumice/Ash

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Felsic Lava Flow: Obsidian (fast-cooling rhyolite)

6.5, 6.6 Igneous rock examples (Extrusive Environments)

• Obsidian is an ideal natural material for making tools

• A takeaway message: the same lava (raw igneous rock material), with the same composition, can take on different appearances depending on when, where, and how it cooled.

6.5, 6.6 Igneous rock examples (Intrusive Environments)

• Extrusive Realm: ash cloud, ash fall, lava flow, ash flow, volcanic debris flow (Intrusive Realm): Magma Chamber

6.5, 6.6 Igneous rock examples (Intrusive Environments)

• Narrow Intrusions: Dikes and Sills

• Dike cuts across layers. Sill pushes between layers

6.5, 6.6 Igneous rock examples (Intrusive Environments)

• Broad Intrusions: Batholiths Yosemite National Park

• Small Intrusion: Pluton

Chapter 7: Sedimentary Rock

Chapter 7. Sedimentary Rock

• Sedimentary Rock: rock formed at or near the surface of the Earth in one of several ways, typically at low temperatures.

• Sedimentary Rock: rock formed at or near the surface of the Earth due to lithification of sediments due to pressure, cementation, etc.. Sediments: loose fragments of rocks or minerals broken off of a host rock. Also refers to fragments that are further broken down due to erosion/transport. Rock: a naturally occurring solid that consists of an aggregate of minerals

• Clastic sedimentary rock: formation

• Lithification: compaction and cementation of sediments to form sedimentary rock

  • Clasts: fragments or grains of pre -existing rock

• Depositional Environment: place and/or conditions where sediments collect

• Weathered Rock: rock that is weakened and/or broken down, but still in place.

• Know what is in lecture about these various erosion/transport environments glacial environment desert environment mountain environment estuarine environment river environment

• Sediment sedimentary rock

• beach/dune sand (desert/river) → sandstone

• mud (estuary) → shale/mudstone

• angular clasts (glacier/mountain) → breccia

• river gravel (river) → conglomerate

• Clastic sedimentary rock: lithification

• Clastic sedimentary rock: lithification

• sediment source sedimentary rock

• sand (beach) → sandstone

• mud (estuary) → shale/mudstone

• cobbles (river) → conglomerate Torrey Pines State Park

• Sediment Sedimentary rock

• Other sedimentary rock: lithification

• corals (shallow marine): limestone,

• plants (marsh/estuary): coal,

• plankton shells (deep marine): chalk

Chapter 8: Metamorphic Rock

Chapter 8. Metamorphic Rock

• Metamorphic Rock: rock that forms when a pre-existing rock undergoes changes due to exposure to high pressures, high temperatures, high shear stresses and/or fluids deep within the Earth.

• New minerals (combinations of elements) New texture (arrangements of minerals)

• squeezing, flattening, cooking, melting shearing, flow

Chapter 8. Metamorphic Rock

• Metamorphism generally occurs at 200 degrees Celsius and hotter, and usually at pressures that are thousands of times atmospheric pressure… which means it happens deep within Earth’s crust.

• 1 bar = atmospheric pressure at sea level, 1 kbar = 1000 bar

Chapter 8.2 Metamorphism Causes and Consequences

• Causes of Metamorphism

• Pressure, shear, heat, compression Direction of preferred orientation

Chapter 8.2 Metamorphism Causes and Consequences

• Shape before shear or flattening with shear

Chapter 8.2 Metamorphism Causes and Consequences

• Heat, shape changes in egg

Chapter 8.2 Metamorphic Rock Examples

• sedimentary rock metamorphic rock

• Limestone Heat Pressure Marble

Chapter 8.2 Metamorphic Rock Examples

• Why do we use metamorphic rock (marble) for buildings rather than its prot