Palagonite ridge formed by subglacial eruption. Langjokull glacier in the background.| J-STAGE
Normal fault at Thingvellir. The boundary between the North American plate on the left-hand side and the Eurasian to the right.| J-STAGE
Lakagigar fissure eruption. The 1783-84 Laka- gigar eruption resulted in a great famine, due to which Iceland lost 20% of its population.| J-STAGE
Reykjavik is a smokeless city. Almost 100% of the electricity and the heating depends upon hydropower and geothermal energy.| J-STAGE
Basaltic lava field, the Svartshengi geothermal power plant (right), and the Blue Lagoon (left).| J-STAGE
Gullfoss waterfall. The two-step cataract has a total drop of 32 m.| J-STAGE
Valley of Eldgja. The 934-40 Eldgja eruption occurred along a 75 km-long fissure.| J-STAGE
The braided course of the Jokulfell downstream from Hofsjokull.| J-STAGE
Dettifoss waterfall. The waterfall is 44 m high. The river water is rich in suspended sediments and the waterfall volume is the greatest in Iceland.| J-STAGE
Jokulsarlon lagoon. The Breidamerkurjokull glacier has been retreating since about 1920. The lagoon formed at the glacial front shows a yearly increase.| J-STAGE
Geyser Strokkur. The geyser erupts at 5-10 minute intervals.| J-STAGE
Earth hummock. Earth hummocks are among the periglacial phenomena. The knoll covered with vegetation is |about 0.5 m high.| J-STAGE

Latest Issue

2023 Vol.132 No.1

Investigating a Sea Arch (Megane Cave) Formed at Mado-Shima Island, San’in Coast

Wave erosion produces a variety of marine cavernous forms along rocky coasts. The San’in Coast is a ria coast composed of extensive rocky cliffs that include more than one hundred marine caves. The cover image shows a sea arch formed at an island composed of rhyolite rocks, which was taken using a camera mounted on an UAV. A small boat (lower-right corner) was used for investigating marine caves at inaccessible sea cliffs or offshore islands. We measured the strength and structure of bedrock from the bow of the boat and launched an UAV from the boat to take aerial images from various directions. These aerial images were combined to produce 3-D models of cavernous forms, from which topography and rock structure were analyzed.

(Photograph: Takuro OGURA, Photographed on September 26, 2022; Explanation: Norikazu MATSUOKA)