Smith Rock VulkanSmith Rock volcano (also known as Sumisu-jima, or Smith Island) is a steep, 136 m high pinnacle rising vertically above the sea surface. It is part of the southern rim of a 9 km wide submarine caldera belonging to a larger seamount.
Numerous submarine eruptions have occurred from the volcano, the last one in 1916. Since the 1970s, changes in sea water color have been observed frequently. In October 1992, a 6-km-long zone of discolored water was observed near the shalow Shirane rock.
Beschreibung:The caldera trucates a 20 km wide seamount and was formed about 60,000-30,000 years ago.
Shirane, a dacitic lava dome, is located inside the sumberged caldera and reaches to 8 m below the sea surface. It is 3 km wide and 800 m high. The shallow Shirane rock mass rises to within 7 m depth below the sea surface and is the youngest part of the volcano.
On the outer flanks of the seamount, basaltic, andesitic and rhyolitic lava flows have been sampled. Two large submarine cones, Sumisu Knolls No. 1 and 2, lie west of the caldera.