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Galápagos–Volcanoes Young and Old

April 14, 2019

The Galápagos islands are an unfinished project of volcano building, perhaps going on for the past 90 million years. A plate of mantle moves southeast above a magma chamber that fountains new rock, creating new land. The result provides the equivalent of a testing ground for evolution of new species.

Here on Isabela Island, Punto Moreno, we clambered over a relatively young lava field, just 300 years since it solidified. Much of it remains smooth and black, barely a trace of soil. Only the marine iguanas, which long ago evolved black coloration to hide against the rock, here can be seen like drops of lava come alive to slither down and hunt for algae.

The lava still has the “ropy” texture of molten rock flowing down the mountain.

An old lava tube had collapsed, from where a flow of lava cooled and solidified on the outside, leaving molten rock to continue flowing out the middle.

During the flow, the various metals within the rock separated out by density, especially iron oxide. The separations led to layers of color, particularly red iron, and yellow.

Different islands formed from different offshoots of the magma chamber–where the metals had already separated. The lava forming Rábida Island had 80% iron, which oxidized to red and crumbled into red grains of sand. Here too the animals must adjust.

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