Located south of the Sea of Okhotsk, for 10 points, identify this northernmost of Japan's four great islands.
Located just north of the Blakiston zoological line, this island's major river was reduced by 100 miles in length by channelization projects and passes through a large valley formed from volcanic tuff called Sounkyo. Also including the large wetland of Kushiro Shitsugen, this island includes the Shiretoko peninsula as well as a large caldera lake at Akan next to the triple-crated Mount Akaen. The south of this island contains the Hidaka Mountains, home to unique brown bear populations. Formerly known as Enzoki, this island contains major brewing facilities in its capital of Sapporo. This home of the Ainu is connected to its southern neighbor by the Seikan tunnel underneath the Tsugaru Strait. Located south of the Sea of Okhotsk, for 10 points, identify this northernmost of Japan's four great islands.
Located just north of the Blakiston zoological line, this island's major river was reduced by 100 miles in length by channelization projects and passes through a large valley formed from volcanic tuff called Sounkyo.
Hokkaido [accept Enzoki before mention] 