Our imaginary flight finally nears the West Coast of the United States. It is a region of active geology (both tectonic and volcanic) and magnificent, varied scenery. The entire coast from Baja California (and into Mexico and Central America) is along an active plate margin. For California, Oregon, and Washington, the tectonic framework is shown in this figure, which plots the location of the great transform fault, the San Andreas, and a subduction zone from northern California past Washington:
The mountain units are part of a vast array of folded and tilted blocks, and accreted terranes that extend from Baja California on the western edge of the North American tectonic plate to well into western Canada northward into southern Alaska. The map below shows the major terranes that were driven onto the western edge of the North American continent. The nature of these terranes is discussed in detail in Section 17, starting with page 17-6. It is worth noting here that all of the western continental edge is an active plate margin. From San Francisco southward the boundary is complex, involving a failure to subduct so that movement is lateral along fault systems (San Andreas et al.). From northern California over most of the remaining coast into Alaska, the boundary is of the subduction type (mostly of the Pacific plate, but from California to southernmost British Columbia a small separate oceanic crustal block, named the Juan de Fuca plate, is subducting and causing the volcanoes of the Cascades to be emplaced as plate scraping produces heat to melt rock.
Our aircraft is headed toward San Francisco. The scene below will introduce you to California - a fabled place to both the Americans and to the world at large. With its 40 million people, its development has made the state the 5th largest economy in the world. Lets take a look at the entire state as seen in one of the early Landsat mosaics made by the General Electric Space Division lab near Beltsville, MD.:
The physiographic/geographic features of California are shown in this map:
Since we will concentrate on California we will set up a geologic framework for that state using this map.
The major physiographic (geomorphic) units for California correlate well with the geologic units:
Entering the state from Nevada, we proceed across the Sierra Nevada Range, the large, strongly glaciated tilt block of crust composed mostly of igneous and metamorphic rocks associated with numerous interpenetrating batholiths. This mountain range rises precipitously to 4,421 m (14,494 ft) at Mt Whitney - the highest point in the 48 states - on its east side (south of this scene). The east side tends to be steep-fronted, being fault-bounded, whereas the western slopes are gentler in inclination, although still deeply dissected by streams. The scene below shows off the northern Sierras with Reno at top center, volcanics in the westernmost Basin and Range appearing in bluish tones, Lake Tahoe nestled in the High Sierras, and many deep valleys. Dark firs and other vegetation persist up to about 2750 m (9000 ft), above which trees are absent and rock bare (light tan).
The Sierra Nevada is impressive as viewed by the astronauts from space. It is also compelling to see from the air. These two images confirm this:
The eastern front of the Sierras rises steeply from the Owens Valley to its east (to the south of the Landsat image. This image was made by combining a SIR-C image with topographic data derived from its altimeter:
Many "westerns" or "cowboy" movies are filmed along the east side of the Sierra Nevadas. The distinctive vegetation (semi-desert) and the gray granite rocks are clues as to the setting being eastern California. This is an example:
The next image shows the section of the east front of the Sierra Nevada that includes Mount Whitney and the town of Lone Pine:
The highest mountain in the continental 48 state is Mount Whitney at 14505 ft. Here it is:
In the high country, glaciation has carved out deep canyons and rugged landscapes. This ground view of the Kings Canyon National Park area to the south shows why it is popular with rock climbers:
One of the best known National Parks is Yosemite. Its most featured visual landmark is the steep-faced (from glacial erosion) El Capitan, seen here from space by the IKONOS satellite:
The foothills of the Sierra Nevada have a notably different topography than the High Sierra:
Both the High Sierra and its foothills were the focal point of the "mad" gold rush of 1849. Gold has been continuously mined ever since. Much gold is found as placer deposits, i.e., found in river wash and sediment as nuggets and grains after being weathered out from the Mother Lode (mostly quartz veins in the granite complex). Active placer mining, using streams of water to wash through the river beds and separate the heavy gold from the sediment, is still going on today. This ASTER image shows the placer piles along the Yuba River in the foothills.
We then pass west over rolling ground in the Sierra Nevada Foothills across the Central Valley into the Coast Ranges around the San Francisco Bay area, all shown in this October, 1972 Landsat image.
The Coast Ranges are generally hills to mountains that are not very high. We saw in Section 1 (Morro Bay) that a hallmark of these ranges is the brown grasses that cover the landscape during all but the rainy season. But woodlands are present in some of the higher areas of these mountains (which have been forming during much of the Cenozoic):
Most of the landmarks we describe next are seen in this high-altitude aerial oblique IR image taken by a camera onboard a NASA U-2 aircraft. The view from this perspective looks east-northeast from a point over the Pacific Ocean. In the distance are the snow-capped Sierra Nevadas and the Sacramento Valley before it. Try to match specific features in this IR photo (which, incidentally, is blue-dominated because the sky blue effect was not compensated by a haze filter) with their counterparts in the Landsat image.
The Central Valley, known in its northern half as the Sacramento Valley (the southern half is the San Joaquin Valley), is one of the great agricultural regions of the world. The numerous farms visible in the above imagery attest to this dominant land use. Cash crops include beans, cotton, rice, barley, and sugar beets. Stockton, Fresno and Modesto are three large valley towns.
The Pacific Coast Ranges are part of the Western Cordillera (sometimes known in Canada as the Pacific Cordillera and also as the Canadian Cordillera), which includes the Rocky Mountains, Columbia Mountains, Interior Mountains, the Interior Plateau, Sierra Nevada Mountains, the , and other ranges and various plateaus and basins. The Pacific Coast Ranges designation, however, only applies to the Western System of the Western Cordillera, which comprises the Saint Elias Mountains, Coast Mountains, Insular Mountains, Olympic Mountains, Cascade Range, Oregon Coast Range, California Coast Ranges, Transverse Ranges, Peninsular Ranges, and the Sierra Nevada Range. The term ''Coast Range'' is used by the United States Geological Survey to refer only to the ranges south from the Strait of Juan de Fuca in Washington to the California-Mexico border; and only the ranges west of Puget Sound, the Williamette valley, the Sacramento and San Joaquin valleys or 'California Central Valley' (thereby excluding the Sierra Nevada and Cascade Ranges).
The Coast Ranges are the most recent products of still active orogeny that results from the collision of the Pacific and North American lithospheric plates. The mountains consist of granular (clastic) sedimentary rocks in places metamorphosed by high temperatures and pressures or intruded by igneous magmas when previously they were buried. Their rocks have been severely deformed, but the ranges generally rise only a few thousand feet above the Pacific sea level. Passing near the coast but inland is the great wrench (horizontal movement) fracture known as the San Andreas Fault (in the Landsat image look for the abrupt termination of red [from California oaks, redwoods, and other vegetation] in the mountains south of San Franciso), which is the plane dividing the north-moving Pacific side of the fault from the more static North American side.
Two coastal bays stand out in the Landsat image: Monterey Bay near the bottom (noted for its rich aquatic fauna and pelagic bird life) and San Francisco Bay, which to its north becomes San Pablo Bay, along which San Francisco (west), Oakland (east), San Jose (south) and many other Bay Area cities are situated. The fault-bounded hills to the east are part of the Diablo Range, which becomes progressively less vegetated towards the Great Valley (at this time of year it is covered with the same brown, dried grasses we examined in the Morro Bay subscene).
Most of San Francisco appears in grayish-blue tones that indicate a sparsity of trees in the city (rather surprising to any resident or visitor who is struck by its great beauty). The exceptions are the lush vegetation (many eucalyptus trees) in Golden Gate Park (long rectangle) and the Presidio (a now deactivated military facility). Your monitor resolution may allow you also to pick out thin (blue) lines of ships (mothballed Liberty Ships and others from World War II) right of the narrow Carquinez Straits off the east end of San Pablo Bay.
In the southern part of the Bay are large patches with lighter blue or green tints. These are salt evaporating basins. The greenish ones are actually basins with red sediments (bright tones in Thematic Mapper Band 3 that thus pass green light in an RGB:432 transparency). A closer look at these basins is afforded by the MISR sensor onboard the Terra spacecraft.
Many consider San Francisco to be the most beautiful city in the U.S. Here is a photo that shows the central city from the tourist vista called Twin Peaks.
Lets take a closer look from space by enlarging the Bay Area portion of the full Landsat image.
It is worth noting that Oakland and San Jose are major cities, with populations greater than a half million each, and both support major league sports.
We carry this enlargement even further to highlight the landmark bridge leading into the Peninsula from the north, the Golden Gate Bridge. The view (lower image) of "the City" through the bridge is from the vantage of a small park on the Marin County side (at X in upper image). The Presidio and Golden Gate Park (rectangle) stand out because of their many trees (eucalyptus is common).
Such a well known landmark as the Golden Gate Bridge is an obvious prime target for high resolution imagery obtained from a satellite. The IKONOS system has produced this 2 meter image of the Golden Gate Bridge:
San Francisco is equally impressive when looking at its east side, from a southeast vantage point across the San Francisco Bay; the span is called the Bay Bridge and extends to the east (right) into Oakland:
A remarkable image of downtown San Francisco with its many tall building (some visible in the above photo) has been taken by the IKONOS satellite (SpaceImaging, Inc.). This color version has a spatial resolution of 2 meters:
Across the Bay near Oakland is Berkeley, the home of the University of California's flagship campus in the northern part of the state.
Before taking leave of the City by the Bay and central California, we present one more interesting Landsat image. It shows the Bay area clear of fog (normally in summer fog rolls in every day) but the Great Valley to the east is entirely fog shrouded. This is the so-called tule fog that often develops inland under the right meteorological conditions. Note that this fog has spilled over the low pass where Highway 50 crosses the eastern Coast Range into the Livermore Valley.
One of the best known places in California - and for many a visual introduction to its beauties - is the Pebble Beach Golf course between Monterey and Carmel, about 100 miles south of San Francisco. Each year a major golf tournament takes place there in winter. Here is a view looking south:
Those living, or visiting, in California - if they have the time - often travel to or from San Franciso to Los Angeles via the famed Highway 1 that follows the coast much of the way. The scenery is spectacular (frequently used in TV commercials). The most scenic stretch is the Big Sur, south of Monterey. Here is a ground view:
Venturing to the southern part of California, we have shown images and ground scenes from the Los Angeles area and around San Diego in Section 4 of the Tutorial. The areas in and around Los Angeles were emphasized. We can see the locations of major cities in the area in this nighttime astronaut photo:
Parts of southern California are quite mountaineous. Here is a scene showing the San Bernadino mountains east of Los Angeles:
Off the shores of Southern California are several large islands, sometimes referred to as the Channel Islands. These are actually the above sealevel tops of largely submarine mountaneous protrusions on the shelf. Santa Cruz Island lies just south of Santa Barbara.
It is appropriate to show one more scene in the southern half of the state - Santa Barbara. This town is often referred to as the "American Riviera" because of its setting with mountains (Santa Ynez Range) as a backdrop. Here are two views of this lovely town:
Let's start to leave the Great State of California to go northward by first traveling up the Sacramento Valley to the state's capital at Sacramento, seen here in two space and one aerial view:
California contains at least one active volcano. Mt Lassen in the Cascades at the north end of the Sierra Nevadas last erupted in 1915. One of the most beautiful of all Cascade Volcanoes is Mt. Shasta (the larger white patch near the top) seen here in a photo taken from the ground looking north and then in an astronaut photo taken from space:
The photo is rather bland. This next image is a processed digital image of a satellite data set in which some of the ground features now stand out owing to their color assignments.
To the west is the scenic coastline of California. The largest town on the coast anywhere north of San Francisco up to the Canadian border is Eureka (population 42000+), seen in this IKONOS image and in an aerial view, which shows how the town is situated on the nearly enclosed Humboldt Bay.
Before leaving the Golden State, look at this: a first-order Landuse/landcover map of the state was produced by the NASA Ames Research Center in cooperation with the NASA Jet Propulsion Laboratory. Here it is (admittedly hard to read at your screen scale):
JPL has a short survey of the various ways that California has been monitored from space. Access through the JPL Video Site, then the pathway Format-->Video -->Search to bring up the list that includes "California from Space", September 6, 2003. To start it, once found, click on the blue RealVideo link.
Whoa! Some viewers of this Tutorial who live in the Pacific Northwest may feel slighted in that we haven't shown any imagery so far that covers their fast-growing region. We can ameliorate this seeming oversight by allowing our airplane to change course in Nevada and head northwest into Oregon. The view below is a mosaic (production of this type of composite scene is treated in the next section) of images covering most of the western halves of Oregon and Washington:
The large river that divides the mosaic is the Columbia which is also the state border between Oregon and Washington. The near vertical set of white patches marks snow found on the higher elevations of the Cascades. The large white circular patch in the Oregon Cascades is Mount Hood, a few 10s of miles south of the Columbia River. North of the river are Mount Rainier and Mount St. Helens, among the numerous active and dormant, variably eroded, stratovolcanoes that make up the High Cascades. In northwest Washington is an E-W body of water off the Pacific Ocean that ends to the east with various islands and several inlets including the N-S Puget Sound along which Seattle is located. Near the upper left is the Canadian island of Vancouver. From the Cascades westward the land is heavily wooded (including abundant firs and other evergreens), as indicated by the widespread reds. East of the Cascades, the land is sparsely covered by trees - a consequence of the rapid reduction in rainfall as clouds pass over the Cascades, dumping their moisture, and producing a so-called "rainshadow" that creates a semi-desert ecosystem.
One Landsat scene in southern Oregon (just below the bottom of the mosaic) contains several features of special interest both within and east of the Cascades. Look:
The focal point in this scene is the circular lake known as Crater Lake (near left center edge). This 12 km (8 miles) wide lake lies within a now extinct volcano, known as Mt. Mazama, that collapsed and erupted violently about 10000 years ago, perhaps before humans lived in the region. Thick ash beds resulted - much more than was expelled from Mt. St. Helens. Here is an astronaut photo of Crater Lake taken from the International Space Station:
In the Landsat image, Klamath Lake lies near the bottom. The blue lake to the east is Summer Lake. The Great Sandy Desert (dark blue) is a series of volcanic flows that are roughly coeval with the Snake River Plains to the east.
When the writer (NMS) first saw this Landsat image, he was struck by the conspicuous large elliptical feature northeast of Crater Lake. It resembled a huge volcanic caldera. Visiting it in 1966 during a field conference on volcanism, I learned that the western part known as the Walker Rim was a cliff composed of volcanic flows. Solid evidence for a caldera was not obvious. This may be a coincidental artifact of several topographic features that because of vegetation distribution gives the impression of ellipticity.
Portland, Oregon lies within the land between the confluence of the Willamette River and the Columbia River. Here this is seen in these two Landsat-7 scenes and then in a perspective view using a Landsat-5 (RGB = 542) subscene looking almost south.
The city is shown in this aerial oblique photo:
Looking east, Portland's skyline is beautifully enhanced by Oregon's tallest mountain, Mt. Hood, a stratovolcano:
Now let us look for a moment at Seattle, Washington, and the embayed land to its west, most hosting residential areas, as seen first in this ASTER image and then in this aerial photo of the waterfront looking northeast (note the Space Needle and Mount Rainier):
West of Seattle is the Olympic Range, one of the most beautiful mountain groups in the 48 states. Here are a space image and a ground scene:
East of Washington's Cascade Mountains lies a broad lowlands which includes the so-called Channeled Scablands (see page 17-4 for an explanation). These show up in the Landsat image as the bands of redder surface that have streamlike patterns. On the ground the scablands are dissected basalt plateau rocks and windblown loess:
On the next page we will continue our odyssey of inspection of states adjacent to the Pacific coast, along with a look at several islands that are U.S. territories.