Underneath that ground is granite. It's part of a bigger area called the Idaho Batholith. "(It) covers around 10,000 square miles across Idaho, and was actually formed from a subduction zone.," ...

“The geology, especially along Highway 55 and parts of Highway 95, is essentially pretty prone to landslides and debris flows because it’s made up of what we call Idaho batholith ...

Much of central Idaho is made of Idaho Batholith granite (approximately 65-100 million years old) and Challis Volcanic rocks (approximately 40-50 million years old). Western Idaho is covered by ...

Idaho Highway 55, a popular road that runs between Eagle and McCall north of Boise, has been named one of the most-feared driving routes in the United States. A recent survey of 3,000 road ...