Simon Boxall, from the National Oceanography Centre, told the BBC that they are: "Five kilometres (three miles) across and typically rising 1.5km (0.9 miles) from the sea floor.
"The terrain of the area around Broken Ridge makes the European Alps look like foothills."
The production of sonar maps ensures the search team's deep-water vehicles do not crash into ridges and bumps in the ocean floor.
MH370 lost contact with air traffic controllers on March 8 while carrying 239 people on a flight between Kuala Lumpur and Beijing. The aircraft last made contact 120 nautical miles off the east coast of the Malaysian town of Kota Bharu.
A huge search operation has continued since the jet's disappearance but so far not a single piece of debris has been found.