Podcast
Questions and Answers
Where does the heat in early Earth come from?
Where does the heat in early Earth come from?
Decay of radioactive elements within Earth and processes associated with Earth's formation
What is the effect of heating on Earth?
What is the effect of heating on Earth?
Differentiation - separation of silicate minerals and metals in rocky outer layer and metallic core
What did the asteroid Chicxulub cause?
What did the asteroid Chicxulub cause?
In the Principle of Superposition, in an undeformed sequence of sedimentary rocks, each bed is ________ than the one above and ________ than the one below.
In the Principle of Superposition, in an undeformed sequence of sedimentary rocks, each bed is ________ than the one above and ________ than the one below.
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Principle of Original Horizontality states that layers of sediment are deposited in a tilted position.
Principle of Original Horizontality states that layers of sediment are deposited in a tilted position.
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Match the following types of unconformities with their descriptions:
Match the following types of unconformities with their descriptions:
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Where do volcanoes typically form?
Where do volcanoes typically form?
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Why do volcanoes not typically occur at transform boundaries?
Why do volcanoes not typically occur at transform boundaries?
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What happens at destructive plate boundaries to form volcanoes?
What happens at destructive plate boundaries to form volcanoes?
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Hot spots can lead to the formation of volcanoes in areas distant from plate boundaries.
Hot spots can lead to the formation of volcanoes in areas distant from plate boundaries.
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Study Notes
Earth's First 2 Billion Years
- Early Earth was hot due to the decay of radioactive elements within the planet and associated with Earth's formation processes.
- The heat comes from the thermal energy contained within the objects that formed Earth, as well as from collisions that caused compression and heating of materials.
- As Earth grew, its gravitational force became stronger, causing material compression and heating.
Chicxulub Asteroid Impact
- The asteroid impact occurred 65 million years ago at the edge of the Yucatan peninsula in Mexico, at the end of the Cretaceous Period.
- The asteroid was around 10-15 km in diameter and produced superheated plasma of over 10,000 degrees.
Heating and Differentiation of Earth
- As Earth heated up, silicate minerals and metals melted, leading to differences in density and the unmixing of Earth's layers.
- This process, called differentiation, resulted in the separation of silicate minerals and metals into a rocky outer layer and a metallic core.
- The movement of these materials also caused the Earth to heat up even more.
Formation of Earth's Layered Structure
- Chemical differentiation led to the formation of Earth's layers, including:
- Iron-rich cores
- Primitive crust
- Mantle
Development of the Atmosphere
- Large quantities of gases escaped from Earth's interior, leading to the development of an atmosphere.
Evolution of Continents and Ocean Basins
- The primitive crust was lost to erosion and other geologic processes, leading to the evolution of continents and ocean basins.
Geologic Time Scale
- The geologic time scale is essential for interpreting Earth's history.
- There are two types of dates:
- Numerical dates: specify the actual number of years that have passed since an event occurred.
- Relative dates: cannot tell us how long ago something took place.
Principles of Relative Dating
- Principle of Superposition: in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.
- Principle of Original Horizontality: layers of sediment are generally deposited in a horizontal position.
- Principle of Lateral Continuity: sedimentary beds originate as continuous layers that extend in all directions until they eventually grade into different types of sediments or thin out.
- Principle of Cross-Cutting Relationship: geologic features that cut across rocks must form after the rocks they cut through.
Unconformities
- Unconformity: a long period where deposition ceased, erosion removed previously formed rocks, and then deposition resumed.
- There are three basic types of unconformities:
- Angular unconformity: tilted/folded sedimentary rocks overlain by younger, flat-lying strata.
- Disconformity: a gap in the rock record that represents a period of erosion rather than deposition.
- Nonconformity: younger sedimentary strata overlie older metamorphic/or intrusive igneous rocks.
Geological Contacts
- Contacts and formations can be used to determine the geological history of an area.
Volcano Formation
- Volcanoes typically form in three settings: constructive plate boundaries, destructive plate boundaries, and hot spots.
- Volcanoes do not typically occur at transform boundaries due to limited magma availability.
Constructive Plate Boundary Volcanoes
- Form where tectonic plates are moving away from each other.
- The Earth's crust is pulled apart, creating a new pathway for rising hot magma to flow onto the surface.
Destructive Plate Boundary Volcanoes
- Form at subduction zones where tectonic plates are moving towards each other and one plate descends beneath the other.
- Example: ocean-continent subduction.
Hot Spots Volcanism
- Form above a mantle plume, or hot spot, where magma rises through the mantle and melts the crust above to form a volcano.
- Can occur in areas distant from plate boundaries, referred to as hot spot or intraplate volcanism.
Hot Spot Track
- A chain of volcanoes forms as a tectonic plate moves over a plume of hot mantle material rising from deep within the Earth.
- Examples: Hawaii-Emperor Hotspot Track and Volcanic Activity along Columbia Plateau – Yellowstone Hotspot Track.
Hawaiian Volcanoes
- Formed as a result of the Pacific plate moving over a hot spot.
- Characteristics: Hawaiian Island Attributes.
Continental Hot Spots
- Formed as a result of a tectonic plate riding over a deep-mantle hotspot.
- Example: Volcanic Activity along Columbia Plateau – Yellowstone Hotspot Track.
- Characteristics:
- Initial surfacing of plume head forms basalts.
- Magma mixes with melted continental crust, forming rhyolite lavas.
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Description
This quiz covers the introduction to Earth's history, including its formation and the first 2 billion years. It explores the sources of heat on early Earth, including radioactive decay and gravitational energy.
