Structures and forms of basaltic rocks in Hawaii

The Hawaiian volcanic mountains are broad shields, built by eruption of many thousands of thin lava flows from zones of fracturing known as rift zones. Most of the summits are indented by calderas formed by collapse. Smaller collapse craters, known as pit craters, lie along some of the rift zones, and the calderas have developed at least partly by the coalescence of pit craters. Grabens lie along parts of the rift zones, and collapse of the edges of the shields has produced high fault scarps facing the ocean.