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Questions and Answers
What is the most common mineral in basalt?
What is the most common mineral in basalt?
What type of volcanic rock is basalt?
What type of volcanic rock is basalt?
Which environment leads to the formation of pillow lava?
Which environment leads to the formation of pillow lava?
What type of basalt forms equidimensional blocks up to about 3 ft in diameter?
What type of basalt forms equidimensional blocks up to about 3 ft in diameter?
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Which tectonic setting is associated with Mid Oceanic Ridge basalt (MORB)?
Which tectonic setting is associated with Mid Oceanic Ridge basalt (MORB)?
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Which is a principal subduction zone associated with orogenic volcanism and plutonism?
Which is a principal subduction zone associated with orogenic volcanism and plutonism?
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What is the main cause of tensional stresses at mid-ocean ridges?
What is the main cause of tensional stresses at mid-ocean ridges?
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What is the average rate of spreading at ocean ridges?
What is the average rate of spreading at ocean ridges?
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What prevents the mantle rocks at mid-ocean ridges from changing from solid to liquid state?
What prevents the mantle rocks at mid-ocean ridges from changing from solid to liquid state?
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What type of magma is primarily formed at mid-ocean ridges?
What type of magma is primarily formed at mid-ocean ridges?
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What is the main characteristic rock texture associated with mid-ocean ridge basalt (MORB)?
What is the main characteristic rock texture associated with mid-ocean ridge basalt (MORB)?
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What percentage of the Earth's oceanic crust has been created by spreading at ocean ridges over the last 200 million years?
What percentage of the Earth's oceanic crust has been created by spreading at ocean ridges over the last 200 million years?
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What type of faulting is apparent at mid-ocean ridges due to the stretching of the newly forming ocean crust?
What type of faulting is apparent at mid-ocean ridges due to the stretching of the newly forming ocean crust?
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What happens when deeper, hotter mantle rocks rise up and approach the surface at mid-ocean ridges?
What happens when deeper, hotter mantle rocks rise up and approach the surface at mid-ocean ridges?
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What type of lava is primarily erupted in response to seafloor spreading along the Earth's mid-ocean ridge system?
What type of lava is primarily erupted in response to seafloor spreading along the Earth's mid-ocean ridge system?
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What causes thinning of the crust at mid-ocean ridges, allowing deeper, hotter mantle rocks to rise up and approach the surface?
What causes thinning of the crust at mid-ocean ridges, allowing deeper, hotter mantle rocks to rise up and approach the surface?
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Study Notes
Basalt and Pillow Lava
- Plagioclase is the most common mineral in basalt.
- Basalt is a type of mafic volcanic rock.
Formation of Pillow Lava
- Pillow lava forms in a submarine environment, characterized by rapid cooling and quenching of lava flows.
Types of Basalt
- Alkali basalt forms equidimensional blocks up to about 3 ft in diameter.
Tectonic Setting of MORB
- Mid Oceanic Ridge basalt (MORB) is associated with a divergent tectonic setting.
Orogenic Volcanism and Plutonism
- The Andean subduction zone is a principal subduction zone associated with orogenic volcanism and plutonism.
Mid-Ocean Ridges
- Tensional stresses at mid-ocean ridges are caused by the upwelling of hot mantle rocks and the subsequent divergence of tectonic plates.
- The average rate of spreading at ocean ridges is about 3-5 cm/year.
- The mantle rocks at mid-ocean ridges are prevented from changing from solid to liquid state by the decrease in pressure and increase in temperature.
MORB Characteristics
- Tholeiitic magma is primarily formed at mid-ocean ridges.
- The main characteristic rock texture associated with mid-ocean ridge basalt (MORB) is fine-grained and aphanitic.
Oceanic Crust Formation
- Over 80% of the Earth's oceanic crust has been created by spreading at ocean ridges over the last 200 million years.
Faulting at Mid-Ocean Ridges
- Normal faulting is apparent at mid-ocean ridges due to the stretching of the newly forming ocean crust.
Mantle Rocks and Seafloor Spreading
- When deeper, hotter mantle rocks rise up and approach the surface at mid-ocean ridges, they undergo decompression melting, resulting in the formation of magma.
- Tholeiitic lava is primarily erupted in response to seafloor spreading along the Earth's mid-ocean ridge system.
- The thinning of the crust at mid-ocean ridges, allowing deeper, hotter mantle rocks to rise up and approach the surface, is caused by the divergent plate motion and the resulting extension of the crust.
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Description
Explore the characteristics and structure of basalt, a dark, heavy, iron-rich, and silica-poor volcanic rock that dominates the world's oceanic crust. Learn about its fine-grained or porphyritic nature and its mineral composition, including calcium-rich plagioclase feldspar and calcium-rich pyroxene.
