8.2: Klamath Mountains

The Klamath Mountains, like the Sierra Nevada, San Gabriel, and San Bernardino ranges, were once much lower than they are now, and their surface features were quite tame and uninteresting. The rivers of that time flowed through broad valleys, portions of which remain as plateau-like shoulders overlooking the deep canyons of the present day.

Physical Geography

There came a time when the region began to rise, and with the increase of slope, the streams began to deepen their channels. Anyone looking at a relief map, may be puzzled to understand why the Klamath River leaves the broad Shasta Valley and flows through the mountains in a deep canyon directly to the sea. If we should fill up the canyon, the Klamath River would first form a lake in Shasta Valley and then break through the lowest point in the rim which leads in a southerly direction past Mt. Shasta to the Sacramento River.

The only way in which we can explain the peculiar features mentioned, is by the supposition that long ago, before the mountains had been elevated to their present height, the lowest outlet to the sea lay directly across the mountains where the river flows now, and that as they rose the movement was so slow that the river was able to cut its channel down, and so maintain its position, until the canyons became 2000 to 3000 feet (about 914 m) deep.

Only three valleys of any size are found within the whole Klamath Mountain region. The most important one is Scotts Valley, then Hay Fork Valley and, last, Trinity Valley. In addition, the canyons widen here and there sufficiently to give room for a little bottomland, and if the soil has not been washed away in hydraulic mining, we are likely to find little ranches. The rest of the surface is mostly made up of steep and rugged mountain slopes terminating in deep canyons.

Figure 8.3: Map of the Klamath River Basin in California & Oregon. 2022. Image by Shannon1 is licensed under CC BY-SA 4.0

The Klamath Mountain group includes several distinct mountain ranges which form the watersheds of the different river basins. The highest and most picturesque of these is the Salmon Mountains, which constitute the divide between the Salmon and Trinity rivers. Several peaks have an elevation of over 9000 feet. This region, in common with the other higher mountain ridges of the Klamath Mountains, was once glaciated. There are, in consequence, numerous little alpine lakes very similar to those in the Sierra Nevada. The snowfall is heavy, and on the north slope of Thompsons Peak, which rises 9345 feet, there is a small glacier.

Scotts Mountains lie between the head of the North Fork of Trinity River and the upper Sacramento. They include Castle Crags, widely known for their striking scenic features.

The Siskiyou Mountains lie north of the Klamath River and partly in Oregon. They include several peaks about 9000 feet in height. The Trinity Mountains form a high, sharp divide between the Trinity River and the Sacramento River. They pass southward into the Yallo Bally Mountains, which lie at the extreme southern end of what we are calling the Klamath Mountains.

The Klamath is the largest river in Northern California, and its largest tributary is the Trinity River. The Klamath t rises in the lake region of Southern Oregon and flows a little south of west across a depression in the Cascade Range, or rather a volcanic plateau, as we shall call this part of it in the following pages, and directly into and through the Klamath Mountains, as we have already seen.

The Sacramento River also cuts across the Klamath Mountain region. Its main source is in large springs near the southwest base of Shasta and flows southerly through a picturesque canyon. Long ago a lava stream swept fifty miles down this canyon, burying the old riverbed. The present stream has cut down through the lava and exposed in some places the gravels of its former channel.

The McCloud River Basin is a smaller sub-section within the Sacramento River Watershed that specifically drains into the McCloud River before it joins the Sacramento River. The McCloud River origin begins with Subsequent lava flows from active volcanoes in the Cascade Range, Mount Shasta and surrounding volcanoes that left behind underground channels and chambers. Rainwater and snowmelt seep through the porous volcanic rock, filtering and collecting in underground reservoirs. These reservoirs eventually erupt as springs at the base of canyon walls, feeding the McCloud River with a constant flow of cool, clean water throughout the year.

The Klamath mountains were lifted to their present position in stages, and at each period of rest the streams, after having established a new grade and ceased to cut down, began to meander on their flood plains and widen their channels from canyons to valleys. Then, when the uplift was renewed, they began to cut down again. River terraces were formed this way, some of which are covered with gravel and are rich in gold.

Physical Geology

The rocks of the Klamath Mountains originated as island arcs and continental fragments in the Pacific Ocean. The island masses consisted of rifted fragments of pre-existing continents and volcanic island masses created over subduction zones. These island masses contain rocks as old as 500 million years, dating to the early Paleozoic Era. A succession of eight island terranes moved eastward on the ancient Farallon plate and collided with the North American plate between 260 and about 130 million years ago. Each accretion left a terrane of rock of a single age. During the accretion, subduction of the plate metamorphosed the overlying rock, as well as produced magma which intruded the overlying rock as plutons. Serpentinite, produced by the metamorphism of basaltic oceanic rocks, and intrusive rocks of gabbroic to granodiorite composition are common rocks within the Klamath terranes.

Figure 8.4: Geologic Map of the Klamath Mountains Region- California. Image by M.B. Miller is used by USDA and is in the public domain.

The Klamath Mountains became known as a mining region, due to the placer sand and gravels, which proved to be very rich. Gold was found both in the gravels of the present streams and in the terrace remains of the older streams. The gravels were often so deep that they could not be worked by ordinary placer methods, so, the only recourse left was hydraulic operations. The gravel bars, as they are often called, are now largely worked out, but at one time hundreds of hydraulic hoses were hurling streams of water with terrific force at the gravel banks and washing their materials into long sluices where quicksilver was placed to catch the gold as it was swept along.

Case Study - Mt. Shasta

Mount Shasta is a volcano at the southern end of the Cascade Range in Siskiyou County. It is connected to its satellite cone of Shastina, and together they dominate the landscape. Shasta rises abruptly to tower nearly 10,000 feet (3,000 m) above its surroundings. On a clear winter day, the mountain can be seen from the floor of the Central Valley 140 miles (230 km) to the south.

About 593,000 years ago, andesitic lavas erupted in what is now Mount Shasta's western flank near McBride Spring. Over time, an ancestral Mount Shasta stratovolcano was built to a large but unknown height; sometime between 300,000 and 360,000 years ago the entire north side of the volcano collapsed, creating an enormous landslide or debris avalanche, 6.5 cu mi (27 km3) in volume. The slide flowed northwestward into Shasta Valley, where the Shasta River now cuts through the 28-mile-long (45 km) flow.

Figure 8.5: Aerial Photo of Mt. Shasta Taken from the International Space Station in 2022. Image by NASA is in the public domain.

What remains of the oldest of Mount Shasta's four cones is exposed at Sargents Ridge on the south side of the mountain. Lavas from the Sargents Ridge vent cover the Everitt Hill shield at Mount Shasta's southern foot. The last lavas to erupt from the vent were hornblende-pyroxene andesites with a hornblende dacite dome at its summit. Glacial erosion has since modified its shape. The next cone to form is exposed south of Mount Shasta's current summit and is called Misery Hill. It was formed 15,000 to 20,000 years ago from pyroxene andesite flows and has since been intruded by a hornblende dacite dome.

There are many buried glacial scars on the mountain that were created in recent glacial periods, of the Pleistocene and Wisconsianian ages. Most have since been filled in with andesite lava, pyroclastic flows, and talus from lava domes. Shastina, by comparison, has a fully intact summit crater without glacial erosion, indicating Shastina developed after the last ice age. Shastina has been built by mostly pyroxene andesite lava flows. Some 9,500 years ago, these flows reached about 6.8 mi (10.9 km) south and 3 mi (4.8 km) north of the area now occupied by nearby Black Butte. The last eruptions formed Shastina's present summit about 3,200 years ago. But before that, Shastina, along with the then forming Black Butte dacite plug dome complex to the west, created numerous pyroclastic flows that covered 43 sq mi (110 km2), including large parts of what is now Mount Shasta. Diller Canyon is 400 ft (120 m) deep and 0.25 mi (400 m) wide, is an avalanche chute that was probably carved into Shastina's western face by these flows.

The last to form, and the second highest cone at, the Hotlum Cone, formed about 8,000 years ago. It is named after the Hotlum glacier at 14,160 ft (4,317m) on its northern face; its longest lava flow, the 500-foot-thick (150-metre) Military Pass flow, extends 5.5 mi (8.9 km) down its northeast face. Since the creation of the Hotlum Cone, a dacite dome intruded the cone and now forms the summit. The rock at the 600-foot-wide (180-metre) summit crater has been extensively hydrothermally altered by sulfurous hot springs and fumaroles there (only a few examples remain).

During the last 10,000 years, Mount Shasta has erupted an average of every 800 years, but in the past 4,500 years the volcano has erupted an average of every 600 years.

Cultural Geography

The Klamath people are a Native American tribe of the Plateau culture area in Southern Oregon and Northern California. The Klamath people lived in the area around the Upper Klamath Lake and the Klamath, Williamson, Wood River and Sprague (Plaikni Kóke - “River Uphill”) rivers. They subsisted primarily on fish and gathered roots and seeds. While there was knowledge of their immediate neighbors, apparently the Klamath were unaware of the existence of the Pacific Ocean, and because of this, it caused the Klamath to live in prolonged cultural isolation. However, the Klamath were known to raid neighboring tribes, such as the Achomawi on the Pit River, and occasionally to take prisoners as slaves.

North of the Klamath tribe lived the Molala people. East of the Cascade Range, also known as the "Mountains of the Northerners," in the Rogue River Valley, lived the Rogue River Athabascan tribe. Further south, along the Pit River, called the "River of the Southern Dwellers," lived the Achomawi people. The Atsugewi tribe resided along the Scott River. In the west and northwest regions lived the Latgawa, known as the "Upland Takelma," and the Takelma/Dagelma, known as the "Lowland/River Takelma." There's a possibility that both these western/northwestern tribes shared the name "Rogue River People."

Figure 8.6: Photo of Klamath People in Dugout Canoes, Early 19^th Century. Image by unknown author is in the public domain.

The natives made southern Oregon their home for long enough to witness the eruption of Mount Mazama, around 7,700 years ago. After Mount Mazamas eruption, it would collapse within itself to create a caldera, which filled with rainwater to form Crater Lake.