Wednesday, May 19, 2010

Volcanoes and Earthquakes

Lava Tube, Santa Cruz Island

The lava formations here in the Galapagos are both beautiful and interesting. Like the Hawaiian islands, these islands formed as the mid-ocean hot spot spewed magma up between the earth's floating tectonic plates. Many volcanic features remain, though on this island they are eroded and changed by earthquakes and vegetation.

Today we walked part-way through a lava tube several million years old. In the lava tube, water marks, perhaps from the ocean entering the tube at some point, made stripes on the walls, and broken up rocks were on the floor. It went on for some distance past where we stopped walking, at a hole in the roof where sunshine lit the way.

The Crater on Santa Cruz Island

Near the lava tube, we also visited a gigantic crater with nearly vertical walls covered with vegetation and bright green water at the bottom. This is another volcanic feature in the alien Galapagos landscape. All volcanic cones, craters, and rocky outcroppings are very old and much affected by uplifts and fissures from later earthquakes.

Deep clefts in the shoreline make for interesting small lagoons and narrow waterways with vertical sides, where people swim and dive. I visited several of them on a boat ride yesterday.

"Las Grieatas" -- A deep crevasse between the cliffs

Deep channel between the rocks

On Floreana Island, where I visited on Monday, I saw several other types of lava formation in the highlands on the volcanic mountainside. Most impressive: narrow fissures between standing walls of lava rock. Pirates and whalers once lived and kept animals between these walls, making various grooves and square holes in the rock to insert fences and barricades. Nearby were lava caves, rather small, formed when the lava made a "bomb" that left a bubble in the molten rock as it cooled. In the 1930s some German families lived in these caves.

Pirate's Rocky Lair, Floreana Island

Lava bomb cave, Floreana Island

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