Mid-Ocean Ridges

Thuan Chau, Yao Yao

JdFR

EPR

SEIRPAR

SWIR

CIR

MAR

Mid-Ocean Ridge

• Underwater mountain system formed by plate tectonics.

• Oceanic spreading center– Valley of rifts running along its spine– Responsible for seafloor spreading

• Magma, which comes out at the linear weakness part in the oceanic crust, becomes the new seafloor when it cools down.

• Longest mountain range in the world 80,000km long (65,000km continuous).

Classes of Ridges• Fast-spreading ridges, like

the East Pacific Rise, the spreading rate is 100 to 200 millimeters per year.

• Slow-spreading ridges, like the Mid Atlantic Ridge, the spreading rate is 20 to 40 millimeters per year.

• Ultraslow-spreading ridges, like the Southwest Indian Ridge, the spreading rate is less than 20 millimeters per year.

Central Indian Ridge:Western regions of the Indian Ocean.Lava flow: 0.51-0.68 km3/yearAverage spreading rate: 1.13 cm/year

Southwest Indian Ridge:Southwest Indian oceanSeparated the African and Antarctic platesAverage spreading rate: 13-18 mm/year

Mid-Atlantic Ridge:Atlantic OceanSeparated Africa and South AmericaAverage spreading rate: 2.5 cm/year

Juan de Fuca Ridge: • (500km long, 8km wide)• Subduction zone, divergent zone, transform

zone. • 1.8 to 3 cm/yr. • frequency of seismic events.

East Pacific Rise:• Volcanic chain – 1,800 to 2,700 m above seafloor • 16 cm/ yr (Chile)• 6cm/yr (Gulf of California)

Pacific Antarctic Ridge:• Divergent tectonic plate boundary located in

the South Pacific Ocean. • Rate of spreading is 54-76mm/yr.

Southeast Indian Ridge:• Intermediate spreading ridge• ~60 to 80 mm/yr