Chapter 3 SG Flashcards
Three types of rocks and explain
igneous, metamorphic, sedimentary
igneous - hardened magma/lava
sedimentary - accumulation of sediments
metamorphic - when igneous and sedimentary rock change shape due to pressure
who proposed the continental drift theory
meteorologist Alfred Wegener
What did Wegener suggest?
Suggested that all landmasses were once united in one supercontinent, which he called Pangaea (“All Earth”) and that over many millions of years the continents broke away from one another, slowly drifting to their current positions.
what is essential to understanding the formation of mountains, earthquakes, and volcanoes
plate tectonics
age of earth
4.6 billion years
what are hot spots from?
magma plume formed under the crust that builds until the magma bursts to form new land (Hotspots are areas of volcanic eruption due to a rising plume of molten material. The molten material may explode out of volcano or ooze out of cracks)
folding and faulting are part of what?
diastrophism
folding - folds, ridges, valleys
faulting - rift valleys, fault block
carbonation results in what type of landscape?
karst landscape
Create a sketch and provide a brief description of the formation process for both a stratovolcano and a shield volcano. Indicate whether each type has effusive or explosive eruptions, and provide a real-world example of each.
Stratovolcano (right):
Formation: Built from alternating layers of lava, ash, and volcanic debris during explosive eruptions.
Eruption Type: Explosive.
Example: Mount St. Helens. (High silica content = high viscosity= restricted flow & buildup High silica content = Explosive)
Shield Volcano (left):
Formation: Formed by the accumulation of fluid lava flows that spread out in broad, gentle slopes.
Eruption Type: Effusive (non-explosive).
Example: Mauna Loa. (Low silica content = low viscosity= flows out of the vent easily Low silica content = Effusive)
Briefly describe the weathering and erosion/deposition of the grand canyon
Weathering: The rocks of the Grand Canyon have been broken down by physical (mechanical) weathering, such as freeze-thaw cycles. Water enters cracks in the rock, freezes, expands, and eventually breaks the rock apart. Chemical weathering from rainwater slightly acidic due to dissolved CO₂ has also weakened the rock, especially the limestone.
Erosion: The Colorado River is the major agent of erosion in the Grand Canyon. Over millions of years, the river has cut down through the rock layers, carving out the canyon. The river’s flow carries away sediments, deepening and widening the canyon. Wind erosion has also contributed, scouring the canyon walls and shaping its features.
Deposition: Eroded material from the Grand Canyon has been deposited downstream, either within the river’s channels or in lower-lying areas outside the canyon. Some material is also deposited in the form of alluvial fans or deltas when the river slows down and can no longer carry as much sediment.
Describe the formation of the Hawaiian Islands, including the following details
The role of the mantle plume and magma layering in the process.
The movement direction of the Pacific Plate and how it affects the formation of the island chain.
Identify which island has active volcanoes and explain why.
Mantle Plume and Magma Layering:
Mantle Plume: A stationary column of hot, molten rock (magma) rises from deep within the Earth’s mantle. This plume provides a consistent heat source that melts the Earth’s crust directly above it, allowing magma to rise through cracks and fissures.
Magma Layering: As the magma reaches the surface, it cools and solidifies, layer by layer, forming the volcanic islands. Over time, repeated volcanic eruptions build up these layers, eventually creating islands that rise above the ocean’s surface.
Pacific Plate Movement:
The Pacific Plate is slowly moving northwestward over the stationary mantle plume. As the plate moves, the hotspot remains in the same location, but new volcanic islands form over it. Over millions of years, this movement creates a chain of volcanic islands and seamounts.
As the plate continues to shift, older islands that formed over the hotspot are carried away from the active volcanic zone, becoming inactive and gradually eroding.
Active Volcanoes on the Island of Hawai’i (Big Island):
The Big Island of Hawai’i is currently located over the mantle plume and has active volcanoes like Kīlauea and Mauna Loa. These volcanoes are still erupting because the island sits directly above the hotspot, receiving a continuous supply of magma.
In contrast, older islands to the northwest, such as Maui and Oʻahu, no longer have active volcanoes because they have moved away from the hotspot.
