Tanegashima Geology

The geology of Tanegashima is both interesting and beautiful. The sedimentary deposits which cover much of the island consist mostly of sandstone and shale. The strata was formed over millions of years as numerous layers were deposited on top of each other. This strata was then compressed and uplifted forming beautiful outcrops which can be seen all around the island, especially along the coast.

Picture - Thin strata of an outcrop at Chikura Caves.

These outcrops are absolutely beautiful on a sunny day as light is reflected off the minerals embedded in the rocks. A great opportunity to take some nice close up pictures to use as a background on your PC. Many of the outcrops contain fossils, although not as many as you might expect in a marine environment. Either way the rock formations are definitely worth a visit.
Sedimentary Deposits

Apparently the consensus is that Tanegashima is composed of mostly sedimentary deposits of the Kumage group dating back some 60 million years, the beginning of the Paleogene period which began 66 million and ended 23 million years ago. These deposits consisted of sand and mud which over time were compressed and eventually became the sandstone and shale evident over much of the island today.

The Paleogene comprises the first part of the Cenozoic Era. Lasting 43 million years, the Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a large group of diverse animals before the Cretaceous-Paleogene extinction event that ended the preceding Cretaceous Period.

Picture - A map of Tanegashima showing the extent of the Kumage group which has been overlain with several other geological formations dispersed throughout the island.

Then approximately 14 million years ago Tanegashima and neighboring Yakushima began to get pushed up due to magmatic activity. The Yakushima granite is an intrusion into the sedimentary deposits of the Kumage group. This intrusion pushed Yakushima up and the island continues to rise even today.

The forces which pushed Yakushima mountains up to their present height of over 1,900 meters (the highest point on the island is Miyanouradake (宮之浦岳), with a height of 1,935 meters (6,348 ft)) had little affect on Tanegashima. In contrast the highest point on Tanegashima is a mere 282 meters (925 ft) above sea level.
Chikura Caves

Probably the best place to really see the effects of geological uplift and erosion is on the southern coast of the island and at the famous Chikura Caves, located at Hamada Beach.

Picture - A rocky section of an outcrop and Chikura Caves.

The caves are particularly interesting because you can see the different sedimentary strata close up. The caves were uplifted and eroded over millions of years into the forms that you see today.
Additional Information

Geological information for Tanegashima was minimal at best, especially in English.

Picture - An outcrop of sandstone with an adjacent layer composed of many different rocks.

The following links provided enough information to at least make this page possible but there is obviously a lot more information out there.
Additional Information