Santiago , also called James, or San Salvador Island, is located in the west central part of the Galapagos archipelago. It is the fourth largest island in the archipelago (following Isabela, Fernandina and Santa Cruz). With the exception of some of the large western volcanos of Isabela and Fernandina, it is the also most volcanically active, with many young flows and cones to be seen, particularly along the south, west, and east coasts. These may even be seen from the summit of Volcan Darwin (above) and from space (right). A number of historic eruptions have been reported over the last 2 centuries. Santiago actually consists of two coalesced volcanos: a typical shield volcano on the northwest end and a low, linear fissure volcano on the southeast end. Suble differences in lava chemistry confirm that there are two volcanos here, and indicate that each has its own plumbing system and each taps a different melting zone in the mantle. The shield reaches an elevation of 900 m (2975 feet) in an area north and west of the center of the island. The northwest highlands also appear to be the oldest part of the island. Lavas from Santiago are as old as 750,000 years, based on K-Ar dating. Elevations on the southeast part of the island do not exceed 250 m (800 ft).

A particularly interesting large, young pahoehoe flow may be seen at James Bay in the northwest, a common tourist stop. When the Beagle visited the area in 1835, Darwin found pieces of quince marmalade jar imbedded in the flow. The year of manufacture of the jars, 1684, was molded in the base of the jars. The flow had overrun a marmalade stash left by buccaneers. This flow, often called the "Marmalade Pot Flow", must therefore have erupted between 1684 and 1835. Even today, the flow remains virtually unvegetated and unweathered and retains its black shiny veneer of basaltic glass. Darwin spent considerable time in this area. His study of the palagonite cones south of James Bay lead to his ideas on the formation of palagonite cones. Darwin also visited the salt lake, located in a crater, about 500 m in diameter, just south of James Bay. The crater itself probably formed as a result of a phreatomagmatic explosion (which occurs when magma and water come in contact and the water flashes to steam). The level of the lake is about 10 m below sea level. It is fed by seawater percolating into it through a system of underground fractures and tubes. Evaporation then increases the salinity. Salt deposits here have been commercially mined off and on middle of the last century.

The young volcanic terrain in the area of Sullivan Bay, at the southeast end of the island, is particularly spectacular. The vista is dominated by the large palagonite cone known as Cerro Inn. Young volcanic features may also be seen on Bartolom� Island, just off shore and a common stop for tour boats. The skyline of Bartolom� is dominated by a large pinnacle-shaped rock which was used for target practice by the US Navy in WW II. A naval artillery shell can be seen still lodged in the upper part of the rock.

As is the case in many places in the Galapagos, life is abundant near the shore. Lava lizards are common on many parts of Santiago, as well as the other islands. Marine iguanas and the brilliant sally light-foot crabs are, of course, present, along with the more unusual Galapagos penquin, blue-footed boobies, and the lava heron. Vegetation in the interior of the island has unfortunately been decimated by feral goats, estimated to number as many as 50,000 or more. Goats have inhabited Santiago since at least 1813, when Caption Porter of the USS Essex allowed four of them to escape. The resulting loss of food sources threatens not only the native vegetation, but the native animals such as the giant tortoise and land iguana as well.