Holes on the ocean floor

Context

Sea explorers, deep in the waters along a volcanic ridge in the bottom of the Atlantic Ocean, found a pattern of holes in the sand.

About

What has been found?

During exploration in the north of the Azores, near Portugal’s mainland, explorers saw about a dozen sets of holes resembling a track of lines on the ocean floor, at a depth of 1.6 miles.
There were four more sightings on the Azores Plateau, which is underwater terrain where three tectonic plates meet.
Those holes were about 1 mile deep and about 300 miles away from the site of the expedition’s initial discovery.

Mid-Atlantic Ridge (MAR):

The Mid-Atlantic Ridge (MAR) is known as a mid-ocean ridge, an underwater mountain system formed by plate tectonics.
It is the result of a divergent plate boundary that runs from 87° N – about 333 km (207 mi) south of the North Pole – to 54 °S, just north of the coast of Antarctica.
Like other ocean ridge systems, the MAR developed as a consequence of the divergent motion between the Eurasian and North American, and African and South American Plates.
In the North Atlantic, it separates the Eurasian and North American Plates; whereas in the South Atlantic, it separates the African and South American Plates.
The peaks of the ridge stand about 3 km (1.86 mi) in height above the ocean floor, and sometimes reach above sea level, forming islands and island groups.
The MAR is also part of the longest mountain chain in the world, extending continuously across the oceans floors for a total distance of 40,389 km (25,097 mi).
The MAR also has a deep rift valley at is crest which marks the location where the two plates are moving apart.