Detroit Seamount - Geology

Geology

After its initial formation 51 million years ago, the volcano was active for 25 million years. Parts of the volcano appear to be older than the oldest volcano in the chain, Meiji Seamount. The 2005 analysis found that the volcano had been active throughout much of the Eocene (circa 52-34 million years ago), and that activity may have extended into the Oligocene (under 34 million years ago). The large difference between the youngest and oldest lavas provides evidence that the Hawaii hotspot migrated far more slowly than it does today; for example, Kohala volcano (the oldest volcano of Hawaii island) first emerged from the sea 500,000 years ago, and last erupted 120,000 years ago, a period of only 380,000 years in comparison to Detroit's 18 million or more years of volcanic activity. The large age difference (51 vs. 34 million years) between the submarine preshield stages and the post-shield rejuvenated stage seems to indicate that volcanoes in the chain can erupt again long after they are believed to be extinct. The volcano is known to have erupted intermediately in an underwater and shallow-water environment.

Detroit Seamount has a wide (100,000 square kilometers) base and rises from the bottom of the abyssal plain to a depth of approximately 1,550 m (5,085 ft); in fact, it is as wide as Hawaii island at the head of the chain. The width of the seamount, as well as the extremely gentle slope, which is very shallow even for a Hawaiian shield volcano, seem to show that the seamount suffered a catastophic collapse sometime in its history; such a collapse is a relatively common event in the growth of Hawaiian volcanoes, caused when the volcanoes grow so fast that they destabilize. A sequence of sediments 800 m (2,600 ft) to 900 m (3,000 ft) thick compose the volcano, in several layers. Some papers refer to only the shallowest part of the volcano as Detroit Seamount, and the rest of the seamount as the "Detroit Rise." The tallest volcanic cones of the seamount peak 1 km (0.62 mi) to 2 km (1.2 mi) above the rest of the seamount.