The U.S. Geological Survey’s article, “Plate Tectonics in a Nutshell,” describes how convection currents can cause hot magma to reach the surface along divergent plate boundaries. Iceland, in fact, is located on the Mid-Atlantic Ridge, which is exactly that type of divergent plate boundary. This is the beginning of the rock cycle where brand new rocks on the Earth’s surface form to replace other rocks that are lost because of the subduction of sinking plates at convergent boundaries, as also described in the “Nutshell” article. What is unique about the process as it appears in McPhee’s story is the speed and violence with which the changes happen. McPhee describes how the fishing island of Heimaey had to be evacuated with little warning due to a gigantic volcanic eruption in 1973. Although the people of Heimaey managed to save the fishing harbor by spraying the hot lava with massive amounts of seawater, almost all of the houses in the village were destroyed. Of course, houses that burn down can always be rebuilt. But the eruption left the village with something more, a brand new gigantic mountain! In addition, people who moved back after the disaster use the still hot lava for a central heating plant, and used the volcanic materials to build new streets and a new airport runway. Here is an example where energy from within the Earth and the rock cycle …show more content…
Los Angeles lies right along the San Andreas fault, which Becky Oskin in an article for the Live Science webpage calls a “strike-slip” fault. As the North American and Pacific plates slide by each other, they push the San Gabriel Mountains higher and higher. But, the rocks making up the San Gabriel Mountains are very old. McPhee quotes geologist Leon Silver as saying “The San Gabes look like a flake kicked around on plate boundaries for hundreds of millions of years” (page 228). Energy from the sun plays a role in the story too. The heat and lack of rain means that there is little vegetation to hold the crumbling rock in place. Then, when rains do occur, they sweep enormous amounts of debris down the sides of the mountains through city streets and even to the front doors of peoples’ houses. A system of debris basins have been built to catch material sliding down before it reaches people’s homes. The debris basins fill up and then need to be emptied. McPhee’s book ends with the strangest scene of all: trucks lugging rocks back up the mountain, where they might slide right back down