Cliffs of Molokai
This photo captures perhaps the largest sea cliff on Earth, the north shore of the island of Molokai in Hawaii. See the big, horizontal-ish layers? Those layers are ancient volcanic eruptions. An eruption like the one going on right now at Kilauea can produce piles of lava that are tens of meters thick, and the volcanoes are built by piling these lava flows one on top of the other.
The cliffs on the north shore of Molokai are, at their tallest, over a kilometer high. The volcanic eruptions that formed this island occurred about 2 million years ago, but the cliffs formed much later. About 1.4 million years ago, a portion of the island of Molokai broke off and slid into the sea, creating what is known as the Wailau submarine landslide. This slide is one of the largest known from the Hawaiian island chain and it traveled nearly 200 kilometers out into the ocean. The slide left a steep scarp at the north edge of the island, seen in this shot. It also likely produced a large tsunami - there is evidence of waves that have traveled hundreds of meters up the slopes of some of the other islands, waves that could have been triggered by a collapse like this one. That steep scarp has since formed large canyons as waterfalls poured over the cliffs, causing the rocks to erode.
Image credit: https://flic.kr/p/cqu7wd
References: https://core.ac.uk/download/pdf/11017798.pdf#page=190 http://www.visitmauiblog.com/blog/geology-of-the-molokai-sea-cliffs/
