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Questions and Answers

What is the primary rock type that makes up the oceanic crust?

  • Limestone
  • Basalt (correct)
  • Granite
  • Sandstone

Which layer of the Earth is directly below the crust?

  • Outer Core
  • Lithosphere
  • Asthenosphere
  • Mantle (correct)

What is the primary characteristic of continental crust compared to oceanic crust?

  • It is thinner than oceanic crust.
  • It consists mostly of basalt.
  • It is generally older and thicker. (correct)
  • It is the only type found under oceans.

What is the Moho Discontinuity?

<p>The boundary between the crust and the mantle. (D)</p> Signup and view all the answers

How thick is the oceanic crust on average?

<p>5 to 10 km (A)</p> Signup and view all the answers

Which part of the Earth does the lithosphere include?

<p>Crust and upper mantle (D)</p> Signup and view all the answers

What percentage of Earth's total volume is made up by the mantle?

<p>84% (A)</p> Signup and view all the answers

What is the primary rock type found in continental crust?

<p>Granite (B)</p> Signup and view all the answers

What is the primary composition of the Earth's oceanic crust?

<p>Basalt (C)</p> Signup and view all the answers

Which of the following layers does not make up the Earth's interior structure?

<p>Surface layer (D)</p> Signup and view all the answers

How does the thickness of the continental crust generally compare to the oceanic crust?

<p>It can be thicker or thinner depending on location. (B)</p> Signup and view all the answers

What percentage of Earth's volume does the crust occupy?

<p>Less than 1% (A)</p> Signup and view all the answers

Which element is more prevalent in the crust compared to the mantle?

<p>Incompatible elements (B)</p> Signup and view all the answers

What classification is used to define the outermost shell of a rocky planet like Earth?

<p>Chemical composition and mineralogy (B)</p> Signup and view all the answers

What is true about the relationship between the crust and the mantle underneath it?

<p>The crust is chemically distinct from the mantle. (D)</p> Signup and view all the answers

What is the primary process responsible for the formation of Earth's crust?

<p>Igneous processes (B)</p> Signup and view all the answers

What is the primary composition of the continental crust?

<p>Granite (C)</p> Signup and view all the answers

Which layer of the Earth is described as the outermost layer?

<p>Crust (C)</p> Signup and view all the answers

Which characteristic accurately describes the oceanic crust?

<p>It is primarily composed of basalt. (D)</p> Signup and view all the answers

What is the density of the continental crust?

<p>2.8 g/cm3 (A)</p> Signup and view all the answers

What material primarily composes the upper mantle?

<p>Iron and Magnesium silicates (D)</p> Signup and view all the answers

The outer core is characterized as being what state of matter?

<p>Liquid (B)</p> Signup and view all the answers

How did Earth's layers initially form?

<p>Through accretion of planetesimals (C)</p> Signup and view all the answers

Which layer is less dense than the core?

<p>Upper Mantle (C)</p> Signup and view all the answers

Flashcards

Oceanic Crust

The thin part of Earth's crust under the oceans, composed of basaltic rock and sediments.

Continental Crust

The thick part of Earth's crust that forms continents, mostly granite.

Moho Discontinuity

Boundary between Earth's crust and mantle, identified by seismic velocity difference.

Lithosphere

Rigid outer layer of Earth, including crust and upper mantle.

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Mantle

Layer between Earth's core and crust, mostly silicate, making up most of Earth's volume.

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Basalt

A common type of volcanic rock found in oceanic crust.

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Granite

A common type of rock found in continental crust.

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Asthenosphere

The upper mantle that deforms easily.

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Earth's layers

The Earth is structured in spherical layers like an onion.

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Earth's crust

The outermost solid shell of the Earth, different from the mantle.

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Igneous processes

Processes that create the Earth's crust from melted rock.

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Incompatibles elements

Elements that don't combine easily and are enriched in the crust.

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Earth's core

Central part of the Earth divided into inner and outer core.

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Earth's Interior Layers

The Earth's interior is divided into several layers: crust, mantle, and core. Each layer has distinct composition and properties.

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What is the core made of?

The Earth's core is primarily composed of iron and nickel. The inner core is solid due to intense pressure, while the outer core is liquid.

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What is the mantle made of?

The mantle is primarily composed of iron and magnesium silicates. The upper mantle is partially molten, while the lower mantle is mostly solid.

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What is the crust made of?

The Earth's crust is the outermost layer, thin and rigid. It is composed of granite (continental crust) and basalt (oceanic crust).

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How did Earth's layers form?

The Earth's layers formed through accretion, a process where smaller planetary bodies repeatedly collided and merged, eventually forming a larger planet.

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What is undifferentiated material?

Undifferentiated material refers to the initial state of Earth's composition before layers formed. It was a homogenous mix of elements.

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What is differentiation?

Differentiation is the process where denser materials sink to the core, while lighter materials rise to the surface, resulting in distinct layers.

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What is the role of the inner core in Earth's formation?

The inner core may have formed first during Earth's accretion, providing a seed for the growing planet, and its gravitational pull attracted more material.

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Study Notes

MARINE ENVIRONMENT

  • Oceanography Geology is the subject matter

Sub-topics

  • Earth internal structure
  • Plate tectonic
  • Seafloor features
  • Marine sediments

Internal Structure of the Earth

  • External shape of the Earth

  • Internal structure and various layers

  • Crust, Mantle, Core

  • Discontinuities (e.g. Moho, Gutenberg, Lehmann)

  • Evidence of Earth's interior structure

  • Earth is not a perfect sphere, but an oblate ellipsoid

  • Equatorial diameter is greater than polar diameter due to rotation

  • The Earth's diameter at the equator is 12,756 km

  • The Earth's diameter at the poles is 12,714 km

  • Layers:

  • Crust (Outermost layer; very thin and rigid; Continental – granite, Oceanic - basalt)

  • Mantle (partially molten; less dense than core)

  • Core (dense; Iron and Nickel; Inner Core - solid; Outer Core - liquid)

Formation of Earth's Layers

  • The Earth formed through accretion, absorbing planetesimals (lumps of rock and ice?)
  • Earth may have accreted undifferentiated material that later separated and formed layers
  • Core formation may have happened before the shell, or a combination of previous planetesimals.
  • The formation of the Earth's layers was due to accretion of undifferentiated bodies

Internal Structure of the Earth (Diagram)

  • The Interior structure of the Earth is layered in spherical shells
  • Earth can be chemically divided into 5 layers (Crust, Upper Mantle, Lower Mantle, Outer Core, and Inner Core)
  • Crust
    • The outermost solid shell
    • Chemically distinct from mantle
    • Richer in incompatible elements than mantle
    • Oceanic ~ 5-10 km; Continental ~30-70 km
  • Mantle
  • Lies between the outer core and crust
  • Average thickness of 2,800 km
  • Makes up 84% of the Earth's volume
  • Solid, but behaves as a viscous fluid in geological time
  • Upper and Lower mantle
  • Core
  • Liquid outer core, and solid inner core
  • Located at approximately 2,880 km beneath the Earth's surface (outer core-mantle boundary).
  • Approx 5155 km beneath the planet's surface, marks the boundary between the inner and outer core.

Moho Discontinuity

  • Boundary between Earth's crust and mantle
  • Defined by contrast in seismic velocity
  • Oceanic crust lies ~5-10 km beneath the ocean floor
  • Continental crust lies ~20-90 km beneath the continents
  • Moho falls within the Lithosphere

Lithosphere and Asthenosphere

  • Lithosphere: rigid outer part of Earth.
  • Includes crust and part of upper mantle
  • Asthenosphere: highly viscous, mechanically weak upper layer of Earth's mantle

Gutenberg Discontinuity

  • Core-mantle boundary of Earth
  • Located approximately 2880 km beneath the Earth's surface

Lehmann Discontinuity

  • Separates the liquid outer core from the solid inner core.
  • Shows abrupt increases in P-wave and S-wave velocities.

Density (p) of Earth's Layers

  • Density increases from ~2.7 g/cm³ in the upper crust to ~12 g/cm³ in the inner core.

Behavior of Earth's Layers

  • SiMA (lower layer of Earth's crust) – rich in magnesium silicate
  • SIAL (upper layer of Earth's continental crust) – rich in silicates and aluminum
  • Core rich in nickel (Ni) and iron (Fe)

Seismic Waves through the Earth

  • Seismology studies earthquakes and elastic waves to understand Earth's structure.
  • Primary (P) waves and secondary (S) waves are used in the study of how different materials affect the distribution of seismic waves

Isostasy

  • State of gravitational equilibrium between Earth's crust and mantle.
  • Adjacent rocks float on the plastic mantle.
  • Thicker blocks extend deeper into the mantle.
  • Oceanic crust is heavier, but less thick, than continental crust

Convection Currents

  • Caused by hot material rising and cooling and sinking in the mantle
  • Circular motion in the asthenosphere that affects the crust
  • Similar to hot water in a pan

Plate Tectonics

  • Plate tectonics is a theory that explains the large-scale motions of Earth's lithosphere
  • The Earth's crust and upper mantle are broken up into numerous sections called tectonic plates.
  • Plate sections are rafts, moving around on mantle

Continental Drift

  • The movement of continents over time
  • Evidence includes similar fossils, matching coastlines.

Seafloor Spreading

  • New oceanic crust is formed at mid-ocean ridges.
  • It explains continental drift in plate tectonics theory

Transform Plate Boundaries

  • Plates slide horizontally past each other.
  • No crust is created or destroyed
  • San Andreas Fault in California is an example
  • There are no volcanoes at transform boundaries

Three Basic Types of Plate Boundaries

  • Divergent – plates move apart
  • Convergent – plates move together
  • Transform – plates move past each other

Convergent Plate Boundaries

  • Oceanic-oceanic
    • Heavier plate subducts beneath the lighter plate, forms volcanoes.
  • Oceanic-continental -Denser oceanic plate subducts, forms volcanoes
  • Continental-continental -Compressing or sliding, creating mountain ranges.

Major/Minor/Micro Plates

  • Seven major plates (area > 10 million km²):
    • Pacific Plate, North American Plate, Eurasian Plate,
    • African Plate, Antarctic Plate, Indo-Australian Plate and South American Plate.
  • More than 9 minor plates (area > 1 million km²): Nazca Plate, South China Sea Plate,
    • Philippine Sea Plate, Arabian Plate, Caribbean Plate, Cocos Plate,
    • Caroline Plate, Scotia Plate, Burma Plate, and New Hebrides Plate.
  • About 60 micro-plates (<1 million km²)

Sea Floor

  • The ocean floor is highly varied, features include mountains, valleys, plains, plateaus in the ocean floor.

Divisions of the Marine Environment

  • Shallow margin – littoral and neritic
  • Deep sea = pelagic

Marine Sediments

  • History
  • Source and composition
  • Distribution (neritic and pelagic)
  • Formation :
  • Sources
  • Terrigenous/lithogenous: Erosion off land (rivers, wind); Volcanic eruptions
  • Biogenous: Shells, skeletons, marine organisms
  • Hydrogenous: Precipitates from seawater
  • Cosmogenous: Space dust, meteorites
  • Amounts of deposits from various sources
  • Compositional type (Terrigenous/Lithogenous, Biogenous, Hydrogenous, and Cosmogenous)
  • Indicators of sediments
  • Distribution of sediment (Neritic and pelagic)

Bathymetry

  • Measurement of ocean depths

  • Also includes charting of ocean floor shapes

  • Methods used to determine ocean floor characteristics

  • History (Lead and line sounding)

  • Modern methods (Echo sounding, sonar, satellite-based radar, submersible surveys, ship-based seismic reflection)

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