Old soils and land surfaces on the Galápagos islands

Summary

Modern rock dating tells that the Galápagos Islands are geologically very young. No rocks have yet been discovered older than two million years. Nevertheless old landscapes with rounded forms exist side by side with more or very recent volcanoes and lava flows and a number of old marine terraces are distinguisable. Red soils have formed only in the old landscapes (high areas of the oldest islands and on the oldest coastal terraces). Their profile has been preserved only in remnants that have escaped erosion. These red soils are the oldest soils on the islands. There are none on the more recently formed W islands. On the other hand, the islands of Baltra, Santa Fé, Española and the flat coastal region of Santa Cruz display a homogeneous marine terrace extensively covered with pebbles and red soil. The said islands are thought to be fragments of submarine lava flows lifted above sea level (Mac Birney and Williams 1969).

The many young marine terraces, on the island of Isabella in particular, show no signs of once having been connected. They seem to have originated as the result of recent tectonic events on the islands or, if they were formed by eustatic sea-level fluctuations, were later moved to their present position by local tectonic activity.