This astronaut photograph highlights the 24-kilometer (15-mile) wide Aso caldera on the Japanese Island of Kyushu. Shadows highlight the caldera rim at image right, while green vegetation covers slopes between the rim and caldera floor at image left.
Aso formed during four explosive eruptions that took place between 300,000 and 90,000 years ago. These eruptions produced pyroclastic flows and airfall tephra that covered much of Kyushu. As the eruptions emptied the magma chambers beneath those ancient volcanoes, they collapsed and formed the caldera.
Volcanic activity continued after the formation of the caldera, as evidenced by 17 younger volcanoes in the area, including Naka-dake—one of Japan’s most active volcanoes and the site of ash plumes as recently as June 2011. The nearby Kusasenri crater is the site of the Aso Volcano Museum and of pastureland for cows and horses.
The floor of Aso caldera is largely occupied by urban and agricultural land uses that present a gray to white speckled appearance. Fields and cities surround the younger volcanic structures to the north, west, and south. Tan to yellow-brown regions along the crater rim—and along the lower slopes of the younger volcanic highlands in the central caldera—are lacking the dense tree cover of some of the greener areas in the image.