This great clifflike formation, rising to an elevation of 9,178 feet, is
to the north of Crater Lake and outside of the park. It is a picturesque
sight when seen from the heights surrounding the lake and is often
referred to as the Matterhorn of the Cascade Range. It is the wreck
remaining of a great mountain. The sharp summit of the peak has been
shattered repeatedly by lightning, producing fused glassy surfaces and
tortuous opening of the nature of fulgurite formations. To reach its
sharp heights is difficult and requires experience in mountain climbing.
Near the foot of Thielsen lies Diamond Lake.