Japan: a country full of geologic activity
Jay and I arrived in Japan on 27 August and will be traveling in the country for 6 weeks. There are many reasons to travel here. The culture and history are fascinating and—wow!—who doesn’t enjoy the high quality food. For two earth scientists, learning more about the country’s geologic makeup is another big draw. In Japan, no one is immune from the potential geologic action of earthquakes, volcanic eruptions, or both. Weather can be very active too, as typhoons (i.e., hurricanes) regularly impact the islands during this time of year. In the six days since we’ve been here, typhoon Shanshan arrived, stalled and pounded southern Japan with high wind and rains, causing destructive landsliding and flooding.
Let’s think about subduction zones
The purpose of this first post is to introduce the islands’ tectonic setting. The primary theme is subduction tectonics, where oceanic plates slide beneath continental plates. Those of us who live in the Pacific Northwest, adjacent to the Cascadia Subduction Zone, are familiar with this type of tectonics. These are the places on Earth where the largest earthquakes and most of the dangerous volcanic eruptions occur. Japan has experienced subduction tectonics for 500 million years, so it has a long and complicated history of continual geologic activity.
Inevitably, subduction zones produce earthquakes and volcanoes. Earthquakes occur when the oceanic plate slips along a fault and sinks farther beneath the continental plate. Volcanoes occur because the down-going oceanic plate causes rocks to melt and ascend all of the way to Earth’s surface where the magma erupts. See my post about converging plates for more details: https://landscapes-revealed.net/plate-tectonics-101-what-happens-when-plates-move-toward-each-other/.
Right-side. The red triangles are active volcanoes that are found along the length of Japan and along the Izu-Bonin-Mariana volcanic island arc that has been created by the subduction of the Pacific plate beneath the Philippine plate. This volcanic arc has been colliding with Japan, creating additional complexity. It’s the elevated ridge on the “Philippine Sea Plate” with green dots (left-side map) that are the volcanic islands. Figure is from the USGS (U.S. Geological Survey).
In Sapporo and heading east to national parks
After two days in Sapporo, we today headed eastward to explore some of Japan’s finest national parks.
Next we’ll visit some national parks with still-active volcanoes. Still tuned!
What a slew of active volcanos in Japan! Looking forward to learning more about the geography of Japan from you two.
We’re off to see a whole string of them today!
Great piece… you must be in seismic heaven! Have a wonderful time in the best travel destination on the planet.
We’ll exchange note in October!