Volcano
The 310,000 km2 (119,000 sq mi) volcano, Tamu Massif, is comparable in size to Mars' vast Olympus Mons volcano, which is the largest known volcano in the Solar System. It was formed about 145 million years ago when massive lava flows erupted from the centre of the volcano to form a broad, shield-like feature. That suggests the volcano produced a flood basalt eruption.