But leaving these inconspicuous craters, let us briefly examine some of the higher mountain peaks of the United States that are of volcanic origin. One of the most conspicuous of these is Mt. Shasta. This mountain is situated in California, at the northern end of the Sierra Nevadas. It has a height of 14,350 feet. It is a snow-clad mountain of a conical form, and is a conspicuous object in the landscape, because it stands alone.
Mt. Shasta is a double-coned mountain. Besides the cone on its summit there is a well-developed cone known as Shastina on the western side of the mountain, 2,000 feet lower than the main summit.
There are well-defined lava streams on the slopes of Mt. Shasta. One of these, which issued from the southern side of the mountain at an elevation of 5,500 feet, divided into two streams. One of these streams is twelve miles in length. The other entered the canyon of the Sacramento River, thus displacing the water.
Coming now to the Cascade Mountains, in Oregon and Washington, we will find in them a number of giant peaks of volcanic origin. The most important of these are in regular order from south to north, as follows: Mt. Pitt, 9,760 feet; Mt. Mazana, 8,223; Mt. Union, 7,881; Mt. Scott, 7,123; Three Sisters, Mt. Jefferson, 10,200, and Mt. Hood, 11,225, in Oregon; Mt. Adams, 9,570; Mt. St. Helen's, 9,750; Mt. Rainier, 14,525, and Mt. Baker in Washington, 10,877.
Nearly all these mountains have craters either on their summits or on their sides. They are extinct volcanic mountains, that were, for the most part, thrown up during the Tertiary Geological Period, so that they have all been greatly affected by erosion.
One of the most remarkable of the above volcanic mountains is Mt. Mazana, in Oregon. This mountain has on its summit an approximately circular cavity from five to six miles in diameter, that is occupied by a lake of water known as Crater Lake. This lake is 6,239 feet above the level of the sea, and has a depth of 1,975 feet. It is surrounded by nearly vertical walls ranging from 900 to 2,200 feet deep, so that the vast caldera of which this great depression consists has a depth of at least 4,000 feet.
Mt. Pitt, situated about sixty miles north of Mt. Shasta, in southern Oregon, has a regularly shaped volcanic cone, and the remnant of a crater at its summit. The Three Sisters and Mt. Jefferson lie to the north of Mt. Pitt. Like the others they are ancient volcanic mountains. But little is accurately known concerning them.