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How do volcanic activity and sedimentation shape the ocean floor?

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Map graphic showing the boundaries of the five oceans-Pacific, Atlantic, Indian, Arctic, and Southern-using color-coded regions. Four different map projections are included: North Pole view, South Pole view, International Date Line view, and Greenwich Meridian view, each displaying the oceans' extents around the continents. — ocean Earth's oceans and their marginal seas cover nearly 71 percent of the planet's surface.

Volcanic activity and sedimentation are primary forces that shape the topography of the ocean floor, constantly altering its relief over geologic time.1

Volcanic Activity

Volcanism is a major constructive process that creates significant seafloor features. At spreading centres along mid-ocean ridges, molten rock from the mantle wells up to form new oceanic crust. Beyond these ridges, volcanic processes produce:12
* Seamounts: Large, typically cone-shaped submarine mountains.34
* Guyots: Flat-topped seamounts that were once at sea level before sinking and cooling.34
* Aseismic ridges: Often formed by volcanic activity.1

Sedimentation

Sedimentation acts as a leveling force, gradually burying rugged terrain. Over time, sedimentation blankets and smooths out faulted mountains and abyssal hills.1
* Turbidity currents: These dense, sediment-laden flows transport material from continental margins to the deep sea, creating turbidites and building expansive, flat abyssal plains.56
* Pelagic sediments: These slowly accumulate across the deep seafloor, consisting of biogenic remains and fine particles like volcanic ash or clay.56