Abyssal hill

An abyssal hill is a small hill that rises from the floor of an abyssal plain. Abyssal hills are the most abundant geomorphic structures on Earth, covering more than 30 percent of the ocean floor. They have relatively sharply defined edges and climb to heights of no more than a few hundred metres, with widths from a few hundred metres to kilometres. A region of an abyssal plain covered in such hills is called an abyssal-hills province, although the hills can also occur in small groups or in isolation. They are most abundant on the floor of the Pacific Ocean, where they are typically 50 to 300 metres high, 2 to 5 kilometres wide and 10 to 20 kilometres long. They may form along the flanks of the East Pacific Rise as horst-and-graben features that stretch out over time, or be areas of thicker oceanic crust generated at a mid-ocean ridge during times of increased magma production.