A billow of smoke arose from the crater below, pushed to the ridge line by a forceful wind. The acrid taste of sulphur hit the back of our throats as we were enveloped in a hazy yellow fog. Wind roaring, we held onto our hats and pulled our scarves up to cover our mouths and noses. Then, just as quickly, the view cleared and the fumes dissipated, swept higher by unseen air currents. Below us, we had another unobstructed view of Mount Aso’s hissing crater, already gathering steam to hurl another smoke bomb. Witnessing the enormous power of planet earth’s most primordial act of creative destruction was an unforgettable thrill!

Mt. Aso is the queen of Aso-Kuju National Park, smack dab in the middle of Kyushu, Japan’s third largest island. She last erupted in 2021 and has been temperamental ever since. Some days, visitors can walk right up to the ancient caldera for a peek inside. In February of 2024, however, she was a little too active, prompting a closure of the popular observatory spot. To see inside one of the world’s largest craters (25 kilometer diameter), we had to hike up to the summit of Mt. Nakadake, a nearby peak.

We started our hike at the parking lot visitor center and made our way upwards along a grassy path on the crater’s periphery. The wind was in our favor, with the smoke blowing in the opposite direction for most of the approach to Mt. Nakadake. The grass soon gave way to pockmarked black volcanic rock, red and yellow silt and ash. We ascended a rather short but steep slope and then descended into the Sunasenri Plain, a black lunar-like landscape of soot and black sand. Crossing Sunasenri Plain, we began the colorful ascent of Mt. Nakadake up to the ridge overlooking the crater.

As we approached the ridge, the colors of solidified magma, minerals, and soot became deeper and more vibrant. Rime ice dusted the summit with a sprinkle of white. We could see hardened lava flows snaking down the mountain like octopus tentacles. Once at the top, it was an easy walk across the ridge to the summit, where we were hit with intermittent blasts of toxic sulfur fumes and brief white-outs…but also some clear and fantastic views of the crater.

From the summit marker, we continued onward over gnarly, rocky terrain for another 30-45 minutes to the summit of Takadake, a little higher up. From the summit of Takadake, the trail continues to eventually circle back to where we first hit the ridge. A little short on time, we opted to simply turn back where we were and retrace the same path. Such an adrenaline rush from start to finish - hiking an active volcano was a thrill! Total distance was 6.75 miles and took us 4 hours.