Izu Peninsula Geopark: five easy volcanic sites to see in a day or two

Do · Izu Peninsula · Published 2026-10-25.

A UNESCO Global Geopark since 2018: Mount Omuro, the Jogasaki coast, Joren Falls, the Ryugu sea cave and Dogashima, with what to look for at each.

UNESCO Global Geopark

since 2018, revalidated 2022

Mount Omuro

580 m, scoria cone, about 4,000 years old

Dogashima tombolo

visible at low tide, March to September

The Izu Peninsula is a rare place where you can see, on land, what happens when a volcanic island collides with a continent. For millions of years it travelled north on the Philippine Sea Plate as a chain of undersea and island volcanoes before docking against Honshu. The result is a landscape of lava cliffs, scoria cones, waterfalls over basalt and sea caves, recognised as a UNESCO Global Geopark in 2018 and revalidated in 2022. Our introduction to the geopark explains the story; this guide picks five sites that are easy to reach and easy to read.

The story in two minutes

Millions of years ago, Izu was a group of undersea volcanoes far to the south. The plate carried them north until they collided with Honshu, roughly 1 million to 600,000 years ago depending on the study, and joined the mainland as a peninsula. Large land volcanoes such as Amagi then grew on top, and a field of small volcanoes in the east, the Higashi-Izu group, still erupts from time to time. Each of the sites below shows one chapter of that story: undersea deposits lifted out of the sea, lava from the young eastern volcanoes, and the work of the waves.

1. Mount Omuro: a volcano you can walk around

Mount Omuro, near Izu-Kogen, is a perfectly shaped scoria cone 580 metres above sea level, formed by an eruption about 4,000 years ago. Walking up the slopes is not allowed, to protect the grass, so a chairlift of about six minutes takes you to the rim, and a path of about one kilometre circles the crater, roughly 250 to 300 metres across, in 20 to 30 minutes. The grass on the slopes is burned every year in a traditional ritual, which keeps the cone bare and green. In 2020 the mountain was designated a national natural monument as a typical example of a volcano that erupted only once. From the rim, on clear days, you can see the Izu islands offshore and Mount Fuji to the north.

2. The Jogasaki coast: where the lava met the sea

The same eruption sent lava down to the sea, where it cooled into the black cliffs of the Jogasaki coast. Waves have since cut inlets, sea arches and caves into it. Walk across the suspension bridge and along the cliff path, and look for the columnar joints and bubbles frozen in the rock. See our guide to the Jogasaki coast.

3. Joren Falls: water over a lava flow

In the Amagi highlands, Joren Falls drops 25 metres over a cliff of basalt with columnar joints on both sides. The lava came from a small volcano on the flank of the Amagi mountains. It is one of Japan's 100 notable waterfalls and a prefectural natural monument, and the clear spring water around it is used to grow wasabi in terraced fields that you can see from the path. The Tokai Bus between Shuzenji and Kawazu stops nearby.

4. Ryugu sea cave: a skylight in the cliff

Near Shimoda, the roof of a sea cave has collapsed, leaving an opening about 50 metres across above a small beach. A short tunnel leads inside, and a footpath loops around the rim in 15 to 20 minutes. From the path above, the hole looks like a heart. It shows how waves exploit the weak layers of volcanic rock; the cave is a short bus ride from Shimoda.

5. Dogashima: sea caves, a tombolo and pale cliffs

On the west coast, the cliffs of Dogashima are made of pale volcanic deposits laid down underwater, then lifted and carved by the sea. Sightseeing boats enter Tensodo cave, a sea cave with a collapsed roof that has been a natural monument since 1935, and from March to September a tombolo, a sandbar about 200 to 250 metres long, appears at low tide between the shore and the Sanshiro islands. Check the tide tables first: the path is covered again as the tide rises. Our guide to Nishi-Izu covers the west coast.

Bonus: the Kawazu Seven Waterfalls

If you are heading south from the Amagi highlands, stop at the Kawazu Seven Waterfalls (Kawazu Nanadaru), a forest trail of about one kilometre past seven falls that flow over lava, from the 30-metre Odaru at the top to a loop bridge at the bottom. It shows the same story as Joren Falls on a smaller scale, with teahouses along the way. Our page on the Kawazu Seven Waterfalls has the walking route.

Tips for a better visit

• Wear shoes with grip: the lava coast and the Dogashima tombolo are rough and often wet.
• Go early on weekends; the Mount Omuro chairlift and the Jogasaki bridge get queues by late morning in high season.
• Look closely at the rock: columnar joints, layers of pumice and the holes left by gas bubbles in lava are easy to spot once you know what to look for.
• Stay well back from cliff edges and never walk the tombolo with a rising tide.

Planning a geopark trip

Omuro and Jogasaki fit in one morning from Ito or Izu-Kogen. Joren Falls is on the way from Shuzenji to the south coast by bus, and Ryugu is a short bus ride from Shimoda. Dogashima is a separate day on the west coast: allow a full day if you travel by bus from Shuzenji, and check the boat schedule and the tide table the evening before. The geopark's museum in Shuzenji has exhibits and maps if you want to understand the bigger picture before you go.