rhyolite

Intrepid travelers can ice climb its namesake feature, hike through glassy frozen caves, or trek through Iceland’s dormant volcanoes and remote rhyolite mountains.

This is shown in the glaciated rock-surfaces of the rim that are covered with layers of pumice and rhyolite.

Granite is an acidic rock corresponding to rhyolite in chemical composition.

The oldest volcanic rock appears to be rhyolite, which peers up in two small hills almost smothered beneath the lake deposits.

Basalt is less siliceous than granite and rhyolite, and contains much more iron, calcium, and magnesium.

Rhyolite and other forms of lava were last spread over the region.