Week 2 Lectures Flashcards
The Earth and How it Works; Earth Processes (Lecture 1)
What is the significance of Abraham Ortelius in 1596?
Abraham Ortelius is known for his work “Theatrum Orbis Terrarum,” one of the earliest modern atlases, first published in 1570. The mention of 1596 could refer to a later edition or reprint.
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What is the significance of Alfred Wegener in 1912?
In 1912, Alfred Wegener published “Die Entstehung der Kontinente und Ozeane” (The Origin of Continents and Oceans), presenting his theory of continental drift, a pioneering idea that later contributed to the development of the modern theory of plate tectonics.
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What is the significance of Marie Tharp in 1961?
In 1961, Marie Tharp, along with Bruce Heezen, created the first comprehensive map of the world’s ocean floor, revealing important features such as the Mid-Atlantic Ridge and rift valleys. This mapping work contributed crucial evidence to support the theory of plate tectonics
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What is the significance of Harry Hess in 1962?
In 1962, Harry Hess published the paper “History of Ocean Basins,” introducing the concept of seafloor spreading. This idea proposed that new oceanic crust was forming at mid-ocean ridges, spreading outward, and played a crucial role in the development of the theory of plate tectonics.
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What is a magnetic field?
A magnetic field is a region surrounding a magnet or a moving electric charge where magnetic forces are observed. The Earth’s geomagnetic field is generated by the movement of molten iron and nickel in its outer core.
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What is the significance of Drummond Matthews, Frederick Vine, and Lawrence W. Morley in 1963?
In 1963, they published a paper titled “Magnetic Anomalies over Ocean Ridges,” providing key evidence for seafloor spreading and supporting the theory of plate tectonics. This work built upon the ideas of Harry Hess and contributed to the acceptance of the plate tectonics theory.
The plate tectonics theory
is a fundamental concept in Earth science that explains the dynamic processes responsible for shaping the Earth’s lithosphere (the rigid outer layer) and influencing geological features and phenomena. Here are key points about the plate tectonics theory:
- Lithospheric Plates: The Earth’s lithosphere is divided into several large and small pieces known as tectonic plates. These plates are rigid and float on the semi-fluid asthenosphere beneath them.
- Plate Boundaries: Interactions between tectonic plates occur at plate boundaries, where three main types of interactions are observed:
-Divergent Boundaries: Plates move away from each other.
-Convergent Boundaries: Plates move toward each other.
-Transform Boundaries: Plates slide past each other horizontally. - Seafloor Spreading: At mid-ocean ridges (divergent boundaries), new oceanic crust is formed as magma rises from the mantle, solidifies, and creates new seafloor. This process is known as seafloor spreading.
- Subduction Zones: At convergent boundaries, one tectonic plate may be forced beneath another in a process called subduction. This leads to the formation of deep ocean trenches, volcanic arcs, and seismic activity.
- Transform Faults: Transform boundaries involve horizontal movement along faults, causing earthquakes. The San Andreas Fault in California is a well-known example.
- Evidence: Multiple lines of evidence support the plate tectonics theory, including the fit of continents (continental drift), the distribution of earthquakes and volcanoes, magnetic striping on the seafloor, and the age of oceanic crust.
Earthquakes, Volcanoes, and Mountain Formation: Many geological phenomena, such as earthquakes, volcanic eruptions, and the formation of mountain ranges, are directly related to plate tectonics. For example, earthquakes often occur along plate boundaries where stress and strain build up due to the movement of plates.
- Plate Motion: The driving force behind plate tectonics is the convective currents in the Earth’s mantle. Heat from the interior causes the mantle material to rise, cool, and sink again, generating the movement of tectonic plates.
- Paleomagnetism: Magnetic minerals in rocks record the Earth’s magnetic field at the time of their formation. The study of paleomagnetism provides evidence for seaf
Wilson Cycle: The Wilson Cycle describes the life cycle of an ocean basin, from its initial formation to its eventual closure and replacement. It involves processes such as seafloor spreading, subduction, and continental rifting.
What is the significance of John “Jock” Tuzo Wilson in 1963?
In 1963, Jock Tuzo Wilson proposed the concept of a “hotspot” in his paper “A Possible Origin of the Hawaiian Islands.” This idea explained the formation of volcanic island chains, suggesting that a fixed mantle plume beneath the Earth’s lithosphere could create a chain of volcanic islands as the tectonic plate moves over the stationary hotspot.
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Types of Plate Boundaries
- Divergent Boundaries
- Convergent Boundaries
- Transform-Fault Boundaries
These plate boundaries play a crucial role in shaping the Earth’s surface, causing earthquakes, volcanic activity, and the creation and destruction of crust.
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Divergent Boundaries:
a) Oceanic Plate Separation: At mid-ocean ridges, oceanic plates move away from each other. Magma rises from the mantle, creating new oceanic crust as it solidifies.
b) Continental Plate Separation: In some regions, divergent boundaries can occur within continents, leading to the formation of rift valleys. As the continental crust pulls apart, new crust forms.
Convergent Boundaries:
a) Ocean-Ocean Convergence: When two oceanic plates collide, the denser plate is subducted beneath the other. This process can lead to the formation of deep ocean trenches and volcanic island arcs.
b) Ocean-Continent Convergence: When an oceanic plate collides with a continental plate, the denser oceanic plate is usually subducted. This can result in the formation of volcanic mountain ranges on the continent.
c) Continent-Continent Convergence: When two continental plates collide, neither subducts due to their similar density. Instead, the intense pressure and folding lead to the formation of large mountain ranges.
Transform-Fault Boundaries:
a) Mid-Ocean Ridge Transform Fault: At mid-ocean ridges, where divergent boundaries exist, transform faults accommodate the horizontal movement between adjacent segments of the mid-ocean ridge.
b) Continental Transform Fault: Transform faults can also occur on continents, where two plates slide past each other horizontally. The San Andreas Fault in California is an example of a continental transform fault.
Divergent Boundaries
- Continental Plate Separation:
-Extension of boundaries; new lithosphere is generated.
-Resultant features include rift valleys, mountains, volcanoes, and earthquakes.
-Example: East African Rift System. - Oceanic Plate Separation:
-Extension of boundaries; new lithosphere is generated.
-Features include submarine rift valleys, underwater mountains, volcanoes, and earthquakes.
-Example: Mid-Atlantic Ridge.
At divergent boundaries, tectonic plates move away from each other, leading to the creation of new crust. The process involves the upwelling of magma from the mantle, which solidifies to form new lithosphere. This geological activity is associated with various landforms and seismic events.
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Convergent Boundaries - Ocean-Ocean Convergence:
Features:
-Oceanic Trench: Subduction occurs when one oceanic plate is forced beneath another. This creates a deep trench in the ocean floor, known as an oceanic trench.
-Volcanic Island Arc: As the subducted plate melts in the mantle, magma rises to the surface, leading to the formation of a volcanic island arc.
-Deep Earthquakes: Subduction zones at ocean-ocean convergent boundaries are associated with deep-seated earthquakes.
Example:
Subduction along the Japan Trench: The Pacific Plate subducts beneath the North American Plate, leading to the formation of the Japanese island arc, deep trenches, and earthquakes.
At ocean-ocean convergent boundaries, the denser oceanic plate is subducted beneath the less dense plate, resulting in the creation of various geological features and seismic activities.
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Convergent Boundaries - Ocean-Continent Convergence
Features:
-Volcanic Mountain Chain: The oceanic plate is subducted beneath the continental plate, leading to the formation of a volcanic mountain chain on the continent.
-Folded Mountains: Compression and intense folding occur as the oceanic plate descends, resulting in the creation of folded mountain ranges on the continent.
-Deep Earthquakes: Subduction zones at ocean-continent convergent boundaries are associated with deep-seated earthquakes.
Example:
The Andes: The Nazca Plate subducts beneath the South American Plate, leading to the formation of the Andes mountain range and associated volcanic activity.
At ocean-continent convergent boundaries, the oceanic plate is usually denser and is subducted beneath the less dense continental plate, causing the creation of diverse geological features and seismic events.
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Convergent Boundaries - Continent-Continent Convergence
Features:
-Crustal Thickening: As two continental plates collide, intense compression leads to the thickening of the Earth’s crust.
-Folded Mountains: The extreme pressure and folding result in the formation of large mountain ranges composed of folded and faulted rock layers.
-Earthquakes: The collision and interaction of continental plates can cause earthquakes, especially in regions where stress is released due to faulting.
Example:
The Himalayas: The collision between the Indian Plate and the Eurasian Plate has led to the formation of the Himalayan mountain range, characterized by extensive crustal thickening, folded mountains, and seismic activity.
At continent-continent convergent boundaries, both plates resist subduction due to their low density, leading to crustal thickening and the creation of impressive mountain ranges along with associated seismic activity.
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Transform-Fault Boundaries - Continental Transform Fault:
Characteristics:
-Lithosphere Neither Created Nor Destroyed: Unlike divergent or convergent boundaries, at transform faults, there is no creation or destruction of lithosphere. The plates slide past each other horizontally.
-Lateral (Transform) Fault: Transform faults are characterized by lateral movement along a fault line, where tectonic plates slide past one another.
-Earthquakes: The horizontal movement along the transform fault results in earthquakes, as stress builds up and is released along the fault line.
Example:
The San Andreas Fault: The San Andreas Fault in California is a continental transform fault where the Pacific Plate and the North American Plate slide past each other horizontally, causing earthquakes.
At continental transform faults, the lithospheric plates move horizontally past each other, leading to the development of transform faults and associated seismic activity, particularly earthquakes.
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Transform-Fault Boundaries - Mid-Ocean Ridge Transform Fault:
Characteristics:
-Lithosphere Neither Created Nor Destroyed: Similar to continental transform faults, at mid-ocean ridge transform faults, there is no creation or destruction of lithosphere. The plates slide horizontally past each other.
-Lateral (Transform) Faults: Mid-ocean ridge transform faults are marked by lateral movement along a fault line, where segments of the oceanic plates move in opposite directions.
-Earthquakes: The horizontal movement along the transform fault results in earthquakes, as stress is released along the fault line.
Example:
The East Pacific Rise: The East Pacific Rise is a mid-ocean ridge where the Pacific Plate and the Nazca Plate slide past each other along a transform fault, causing earthquakes.
At mid-ocean ridge transform faults, the lithospheric plates undergo horizontal movement, leading to transform faults and associated seismic activity, particularly earthquakes.
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Mid-Atlantic Ridge:
Type of Plate Boundary:
-Divergent Boundary: The Mid-Atlantic Ridge is a divergent boundary where tectonic plates are moving away from each other, allowing magma to rise from the mantle and create new oceanic crust.
Key Characteristics:
-Length: Approximately 16,000 kilometers, making it the longest mountain range on Earth.
-Spreading Rate: The ridge spreads at a rate of 1 to 10 centimeters per year as new oceanic crust is formed.
-Rift Width: The rift at the Mid-Atlantic Ridge currently spans 80 to 120 kilometers.
Geological Features:
-Volcanoes: The ridge is associated with volcanic activity, and underwater volcanic eruptions contribute to the formation of new crust.
-Earthquakes: As tectonic plates move apart, earthquakes can occur along the Mid-Atlantic Ridge.
-Hydrothermal Fields: Hydrothermal vents and fields are found along the ridge, where seawater interacts with hot rocks from the Earth’s mantle, creating unique ecosystems.
The Mid-Atlantic Ridge is a significant geological feature that plays a crucial role in the process of seafloor spreading, contributing to the creation of new oceanic crust.
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What was the Great Ansei Earthquake of 1855?
The Great Ansei Earthquake of 1855 was a major seismic event that occurred on December 23, 1855, in the region of Edo (Tokyo) during the Edo period in Japan.
The earthquake had an estimated magnitude of approximately 7.0 to 7.2.
The epicenter was near the Sagami Trough off the coast of Sagami Bay, believed to have occurred along the Sagami Trough subduction zone.
What were the main impacts of the earthquake?
The earthquake caused widespread damage to Edo and the surrounding areas, triggering a significant tsunami, widespread fires, and resulting in a considerable number of casualties.
The disaster prompted discussions and efforts to improve earthquake resilience and disaster preparedness in the region, influencing modern earthquake resilience strategies in Japan.
What is a seismometer?
A seismometer is an instrument that detects and measures ground motion caused by seismic waves, providing information about earthquakes.
The primary purpose of a seismometer is to record and measure the vibrations of the Earth caused by seismic events, such as earthquakes.
What is a seismogram?
A seismogram is the graphical representation or record produced by a seismometer, illustrating the amplitude and frequency of seismic waves over time.
A seismogram provides information about the characteristics of seismic waves, including their amplitude, frequency, and duration, which is crucial for studying and understanding earthquakes.
What are compressional waves also known as?
Compressional waves are also known as P waves.
How do compressional waves propagate?
Compressional waves (P waves) propagate by compression and rarefaction, causing particles to move parallel to the direction of the wave.
