Puerto Egas, Santiago Island
The Galapagos Archipelago is often considered a true Mecca for geologists. They are very young islands, on a geological time frame, ranging from just 300,000 years of age to about 4 million years. It is also thought that there may have been a couple of older islands that have since disappeared below the surface of the ocean. Molecular clock aging of certain animal species, such as the endemic land and marine iguanas, suggest a speciation having begun as long as 15 million years ago.
The islands are located on an axis that spreads from west to southeast, due to the movement of the Nazca tectonic plate over a very active hotspot. The archipelago continues below the waters as the Carnegie Ridge, several of whose sea mounds may have once been above waters.
These remote islands are very arid, which means that the volcanic features are extremely visible, and have often been described as a "textbook of geology". Santiago Island is the fourth largest of the group, and is considered one of the "middle-aged" islands, being about 1.7 million years of age. The last recorded eruption here was just over a hundred years ago, so the island may in fact still be considered active. In the past it definitely was a very active volcano, as the fascinating colors and textures of the many volcanic features suggest.
The walk along the shoreline of Puerto Egas, thus named after one of the most recent settlers, is a brilliant example of this. The shoreline is a mixture of tuff stone formations superimposed on basaltic lavas, giving rise to fascinating shapes carved into soft rock, nooks and crannies that the marine iguanas love to bask in. Tuff is a soft sedimentary rock that forms along the shores, when hot lava flows come into contact with the cool Pacific waters. This contact gives rise to phreatomagmatic explosions that pulverize the lava and cause layer upon layer of ash to pile up and later become cemented by a process of litification into a kind of sandstone. This easily eroded rock that layers the coast was then slowly carved, over the years, into the weird formations found along our afternoon walk, by the action of the waves beating and swirling along these exposed shores.
The Galapagos Archipelago is often considered a true Mecca for geologists. They are very young islands, on a geological time frame, ranging from just 300,000 years of age to about 4 million years. It is also thought that there may have been a couple of older islands that have since disappeared below the surface of the ocean. Molecular clock aging of certain animal species, such as the endemic land and marine iguanas, suggest a speciation having begun as long as 15 million years ago.
The islands are located on an axis that spreads from west to southeast, due to the movement of the Nazca tectonic plate over a very active hotspot. The archipelago continues below the waters as the Carnegie Ridge, several of whose sea mounds may have once been above waters.
These remote islands are very arid, which means that the volcanic features are extremely visible, and have often been described as a "textbook of geology". Santiago Island is the fourth largest of the group, and is considered one of the "middle-aged" islands, being about 1.7 million years of age. The last recorded eruption here was just over a hundred years ago, so the island may in fact still be considered active. In the past it definitely was a very active volcano, as the fascinating colors and textures of the many volcanic features suggest.
The walk along the shoreline of Puerto Egas, thus named after one of the most recent settlers, is a brilliant example of this. The shoreline is a mixture of tuff stone formations superimposed on basaltic lavas, giving rise to fascinating shapes carved into soft rock, nooks and crannies that the marine iguanas love to bask in. Tuff is a soft sedimentary rock that forms along the shores, when hot lava flows come into contact with the cool Pacific waters. This contact gives rise to phreatomagmatic explosions that pulverize the lava and cause layer upon layer of ash to pile up and later become cemented by a process of litification into a kind of sandstone. This easily eroded rock that layers the coast was then slowly carved, over the years, into the weird formations found along our afternoon walk, by the action of the waves beating and swirling along these exposed shores.
