GeologyLesson 1 of 1 in the course Plate tectonics

Mid-Ocean Ridges: Spreading, Crust Formation, and Global Effects

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

A mid-ocean ridge is a vast underwater mountain system formed where tectonic plates move apart. This lesson introduces the ridge system, how it fits into ocean basins, and why it is considered the longest mountain range on Earth.

A mid-ocean ridge (MOR) is a long seafloor mountain system formed by plate tectonics. It marks a divergent plate boundary, where two plates move away from one another and new ocean floor is created. At the spreading center, the seafloor is typically about 2,600 meters below sea level and rises roughly 2,000 meters above the deepest parts of an ocean basin.

All flashcards

Mid-ocean ridge
A seafloor mountain system at a divergent plate boundary, where new ocean floor forms.
Global oceanic ridge system
The connected ridge network extends about 80,000 kilometers across the oceans.
Isostasy
The effect of differences in material density and thickness on the elevation of the crust they support.
Mid-ocean ridge basalt (MORB)
Tholeiitic basalt formed at mid-ocean ridges, generally low in incompatible elements.
Fracture zone
An inactive trace of a former transform fault.

Quiz questions

  1. What physical change initiates partial melting beneath a spreading ridge?Answer: Pressure drops as hot mantle rises beneath separating plates.
  2. What spreading rate defines an ultraslow-spreading ridge?Answer: Below 20 millimeters per year.
  3. How do scientists use marine magnetic anomalies to estimate ocean-crust age?Answer: They match magnetic bands to the dated sequence of magnetic reversals.
  4. How can faster spreading contribute to higher global sea level over long periods?Answer: Broader ridges occupy more basin space and displace more seawater.
  5. How does faster spreading affect seawater chemistry and carbonate precipitation?Answer: It lowers seawater Mg/Ca and favors low-magnesium calcite.

Based on the Wikipedia article Mid-ocean ridge, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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