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20 Geological Characteristics of Mid Ocean Ridges

by Dwi Purwaningsih

Ocean dominates the surface part of the earth. The richness of ocean is something experts are exploring for years. The diverse spread of each water part makes the geological characteristics of each ocean an interesting object to study.

One of interesting part in an ocean is ocean ridge. Ocean ridge is interconnected system of volcano series under the sea. Mid ocean ridges extend to 40,000 miles that encircles the earth. Mid ocean ridge is the third biggest ocean phenomenon after continent and ocean basins. Since it consists of volcano series, it has distinct and diverse geological features. Here are 20 geological characteristics of mid ocean ridges.

1. Formed from Fracture Zones

Despite encircling the earth and make a long line of ocean ridge, ocean ridge itself does not come in the form of straight and defined line. Instead, the mid ocean ridges consists of series of fracture zones that in result forms mid ocean ridge. The fracture zone in ocean ridge usually occurs in every 55 kilometers interval.

Fracture zones are the result of weak continent long before the major continent broke apart. The leftover of this is fracture zone. The scattered fracture zones begin to create a pattern and that is how ocean ridge formed. Therefore, mid ocean ridge is not a connected line but a pattern from fracture zones of plate tectonics.

2. Almost Symmetrical Cross Section

Mid ocean ridges encircle the ocean with its long winding series of undersea mountains. In each of the crossing line, it has almost symmetrical cross section. Though not overly identical, this pattern seems to be constant. The cross section may differ between slow spread and fast spread ridge but the shape is almost identical.

The most possible explanation is because undersea volcanoes have almost the same mechanism why they were formed. The forming of undersea volcano is when the earth plates are colliding and magma with volcanic activity is trapped in between. The remnant of it creates ocean ridge. Since the mechanism is similar, the cross section is also almost symmetrical.

Also read: General Characteristics of Coastal Ocean

3. Different History, Different Shape

Even though the mechanism of how a mid ocean ridge formed is similar, the history of its on-going existence will create different shape of each. It can be either from the volcano activity, the amount of magma, or the position of the fracture.

Mid ocean ridge coming from a strong plates collision will have higher while those who did not will have a narrow shape of mid ocean ridge. The one that is formed from the tectonic activity also have its own different speed.
The slow speeding ocean ridge has different shade then the more active and fast spreading one. Also, the strength of the ocean crust when the forming of ocean ridge taking places also proves to affect the shape of mid the ocean ridges.

4. The Depth of Ocean Ridge

The depth of mid ocean ridge is determined by how old the ocean crust is. The study proves that the deeper the ocean ridge, the older the age of the ocean crust. The most logical explanation to explain this theory is because the thermal contraction of the ocean crustes with the upper mantle. The thermal contraction leads to possibility to the older ocean crust with hotter temperature compared to the upper one that has the sea cooling it down a little.

Also, the more a tectonic collision happens earlier, the more the ocean ridge created earlier than the rest of the mid ocean ridge. The activity formed the ocean ridge before other geological process takes place. Thus, the depth of ocean ridge indeed correlates with the age of the ocean crust.

5. Slow Spreading Speed

The mid ocean ridge belongs to ocean ridge that takes slow spreading speed. It means the series of undersea volcanoes fracture has slower pace in the formation of its pattern. The opposite of mid ocean ridge is the East Pacific Rise that belongs to the fast spreading speed ocean ridge.

It has the correlation with the transgression of ocean water. Back in the past, mid ocean ridge has faster pace of spreading but ocean basin also exists as the result of tectonic activity. Thus, now most mid ocean ridge belongs to slow spreading speed phenomenon. The one with fast spreading speed also tend to have overlapping spreading centers compared to the slower one.

6. Has Rift Valley

For slow spreading speed mid ocean ridge, the speed creates rift valley. The rift valley is located at the crest as a result of the fault-controlled process of mid ocean ridge formation. At the intermediate rates of speed, the height of the rift valley is around 200 meter. The height may vary depend on the geological structure and the speed of the spreading.

For the fast spreading speed, instead of rift valley, the process creates axial high at the crest. The slow spreading ocean ridge has rough topography. While the fast spreading East Pacific Rise has smoother flanks than the slow spreading speed. This proves more geological process takes place in slow spreading ocean ridge.

7. Flanks Parallel to The Ridge Trend

The flank consists of several mountains and hills. It elongates in accordance to the ridge trend. Thus, the more the ocean ridge pattern becomes complicated, the more flanks elongate the ocean crust. The flanks also appear more in the rugged topography than the one with smoother surface.

The transform faults are offset across the crest of the ridge. The rough flanks of the slow spreading ocean ridge make it possible to find a more various geological shapes takes place. Thus, the slow spreading mid ocean ridge has more flanks than the rest of them. The flanks comes in many shape and size but with similar features that differ them from other mid ocean ridge features.

8. Formed New Oceanic Crust

The new oceanic crust and the one belongs to the upper mantle of the earth takes place at the crests of mid ocean ridges. Because of this, there can be found many unique geological shape in the crest of ocean ridge. It happens more frequently to the slow spreading ocean ridge in which the formation process takes time and in result, the triggered land creates other geological shapes.

It is important to note that oceanic crust that belongs to the upper mantle also a part of the earth litosphere. Therefore, the ocean ridge plays important role in the formation of litosphere and the geological phenomena (valley, axial high, etc) it created. (Related to Common Hydrodynamic Characteristics of Ocean).

9. Has Fresh Basaltic Lavas

Mid ocean ridge with active tectonic activity has fresh basaltic lavas. The lavas spread on the seafloor of the ocean ridge crest. However, the lavas may not so apparent as sediments of the seafloor spreads out. Still, the heat of the ocean ridge is greater than any other crust on the earth.

The basaltic lavas may reach out the surface when there is a more active volcanic activity takes place at the series of mountain in the ocean ridge. Despite the heat, the lava will only surfaced at the sea level unless a volcanic earthquake takes place. Not every volcano mountain is active and they may have the lava all sedimented. The sedimented lava will create sedimentary rock under the sea.

10. High Amplitude Magnetic Anomaly

The active volcanic and tectonic movement that lie under the mid ocean ridge may create an anomaly where there is high amplitude magnetic. The reason why this anomaly happens is because the geomagnetic field magnetizes the lava on the center crest of ocean ridge.

When this phenomenon happens, the strong magnetic will pull on things around them and influence the tide of the sea. This phenomenon, however, does not happen frequently and is considered an anomaly. The high amplitude magnetic lasts when the geomagnetic field is back with its usual course of activity.

Other geological characteristics of mid ocean ridges are:

  • High chance for volcanic earthquake in active mid ocean ridge
  • Diverse relief from sediment marine organism
  • Basic mid ocean ridge in Atlantic ocean
  • Generally no rift valley in South Atlantic
  • Rugged mountainous flanks in Indian Ocean
  • Low topographic rise in Pacific Ocean ridge
  • Interrupted development of ocean ridge in East Pacific
  • Can have overlapping spreading centers
  • May contain unidentified biological communities
  • Can emanate warm spring in several neovolcanic location

Mid ocean ridges are ocean features that are still the subject of interesting discovery. There may be many unidentified or undiscovered phenomenon that will reveal the richer life of oceanic world. Due to some volcanic activities, experts need a more advanced and accurate technology to keep track of the activity. Mid ocean ridges are ones of many ocean features that may have a lot more than what they appear to be.

It will need more research to discover the rest of the phenomena suspected may be going on under the sea. The characteristics listed are only the observable one in which experts had found the facts from studies and observation. Indeed, there are 20 geological characteristics of mid ocean ridges.

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