Lava on Galapagos

Lava flows are streams of molten rock that pour onto the Earth's surface from an erupting vent. Both moving lava and the resulting solidified deposit are referred to as lava flows. Lava flows come in a variety of shapes and sizes. They are impacted by the wide range in speeds of the different lava types (basalt, andesite, dacite, and rhyolite), the lava discharge during eruptions, and the characteristics of the erupting vent and topography over which lava travels. Fluid basalt flows like those in the Galapagos can extend tens of kilometres from an erupting vent. The leading edges of basalt flows can be as fast as 6 miles (10 km) per hour on steep slopes but they typically travel less than 1/2 mile (1 km) per hour on gentle slopes. When basalt lava flows are confined within a channel or lava tube on a steep slope, the main body of the flow reaches speeds more than 18 miles (30 km) per hour.

Lava, the material expelled from the volcanoes is present in the Galapagos and takes a variety of forms. On Santiago it is possible to see 2 distinct types of lava patterns.

Pahoehoe is a Hawaiian name for basaltic lava that has a smooth, hummocky, or ropey surface.

A pahoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. The surface texture of pahoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture.

`A`a (pronounced "ah-ah") is a Hawaiian name for lava flows that have a rough rubble-like surface composed of broken lava blocks called clinkers. The incredibly spiny surface of a solidified `a`a flow makes walking very difficult and slow. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels down slope, the clinkers are carried along at the surface. At the leading edge of an `a`a flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an `a`a flow.

Tuff Cones - Pinnacle Rock on Bartolome has become one of the most photographed sights in the islands. The Tuff Cone is a vertical rock formation created by the consolidation of hardened ash. During the eruption hot lava reached the sea causing an explosion. Particles splattered down in the shape of cone often known as a Tuff Cone or Cinder Cone.

Lava Tubes - Exploring the Lava Tubes in the highlands of Santa Cruz makes an interesting and eerie adventure. These giant wormholes are caused when the exterior portion of a pahoehoe lava flow hardens while the interior lava continues to flow. Eventually the lava flow diminishes and there is not enough lava left to fill the hollow tube.

Calderas & Fumaroles - A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir. The removal of large volumes of magma may result in loss of structural support for the overlying rock, thereby leading to collapse of the ground and formation of a large depression. Calderas are different from craters, which are smaller, circular depressions created primarily by explosive excavation of rock during eruptions.

Of the many specific geologic features of interest in the Galapagos, Isabela is the only island in the chain created by the merging of 6 volcanoes. A 3 to 4 hour hike up the island takes visitors to one of the largest calderas in the world at 6 x 5 miles (10 x 8 km) on Sierra Negra and to see the Fumaroles or “steam valves” being released from the active crater.