Image: Ikluft
The name of the San Andreas Fault precedes itself like, well, an immense and unavoidable rift in the earth’s surface. Running some 1,300 kilometres through the US state of California and reaching a depth of 15 to 20 kilometres, the San Andreas forms the tectonic boundary between the Pacific and North American Plates. Yet because of its vast size, it’s difficult to grasp this giant geological feature; except, that is, when you look at it from above.
The reason the San Andreas Fault is so famous – or perhaps infamous – is because of the major earthquakes for which it has been responsible. Names like the great 1906 San Francisco Earthquake, which left 3,000 dead, or 1989’s Loma Prieta earthquake, which killed 63, leave some trembling at the thought of the next big one. Worrying, a study suggests that the fault is set for just such a super quake of magnitude 7.0 or over, with the risk rising faster than was previously believed.
The San Andreas fault’s momentous historic earthquakes have together caused hundreds of kilometres of breaks in the earth’s surface. One of the longest and most active faults in North America, the San Andreas was nevertheless only identified in 1895 by Berkeley geology professor Andrew Lawson. After the fateful 1906 San Francisco earthquake, it was Lawson too who realised that the fault extended into Southern California through locations like the magnificent Carrizo Plain.
Breathtaking views: Carrizo Plain southeast along the San Andreas Fault
Image: R E Wallace, USGS
This beautiful aerial shot shows the San Andreas Fault advancing southeast through the Carrizo Plain. In the foreground, the block on the west side of the fault, right, has been raised up due to plate movement, damming the drainage of water running down from the hills to the east, left.
This equally majestic photograph, rich in the colours of Fall and shot from greater distance, shows a northwest view of the San Andreas in the Carrizo Plain. Notice how the upraised block of land on the right eventually gives way to the upraised block on the left in the distance.
The next pastel-coloured shot is a southwest view that depicts a deeply eroded valley along the San Andreas. The downstream segment of the channel on the far west side of the fault has been displaced a kilometre or more from the upstream segment, which is out of view to the left
Panorama supreme: The fault line arcs into the distance
Image: Ikluft
An incredible image showing an aerial view of the San Andreas Fault as it cuts through the Carrizo Plain, photographed from an altitude of 8500 feet.
In this aerial view of San Luis Obispo County from 1965, the Carrizo Plain lies to the right of the Elkhorn Scarp and Elkhorn Plain to left. A scarp is defined as land displaced by movement along a fault, and the Elkhorn Scarp defines the trace of the San Andreas Fault along much of its length through these plains.
Thrown off course: Stream offset by the San Andreas Fault
Image: R E Wallace, USGS
Another aerial shot from the vaults of 1965, this photo shows that running water is no match for a 20 million year-old fault: a stream has been offset by a quarter of a mile by the fault as it travels through Carrizo Plain. Practically all the images collected here show the San Andreas on its journey through the Carrizo Plain, a long, treeless expanse in which much of the fault line is plainly visible.
Yet Carrizo Plain is just one section of the Southern segment of the San Andreas, which bends south and east past the San Gabriel and San Bernardino mountains as far as the Salton Sea lake in the Colorado Desert. The Central segment stretches northwest between the towns of Parkfield and Hollister. The Northern segment, meanwhile, runs through the Santa Cruz Mountains, on up the San Francisco Peninsula, heading offshore at Mussel Rock, before returning onshore once more at Fort Ross – only to go offshore again for some distance before it terminates. Phew.
San Andreas from space: The fault line at Palmdale, CA
Image: NASA
This image from space gives an even greater sense of the scale of the San Andreas, visible as the prominent line passing straight through the centre of the picture. The Pacific plate on the left is slowly moving away while the North American Plate is moving towards us in what is known a right lateral strike-slip fault, the movement of which is horizontal.
Another space perspective: The San Andreas
Image: NASA/JPL/NIMA
The clearly marked feature running down the middle of this impressive view is the San Andreas once again. This segment of the fault lies west of the city of Palmdale, about 100 kilometres northwest of Los Angeles. Two large mountain ranges are in shot, the San Gabriel Mountains on the left and the Tehachapi Mountains in the upper right. Another fault, the Garlock, lies at the base of the Tehachapis.
Mission: Shuttle radar topography
Image: NASA/JPL/NIMA
Like the other images from space included here, this image was created using data from NASA’s Shuttle Radar Topograpy Mission (SRTM), which is being used by geologists to study fault dynamics and physical features in the land that result from shifting plate tectonics. Quail Lake Reservoir sits in the depression created by past movement along the fault.
Psychedelic spectacle: The fault along the southwestern edge of the Mojave
Image: NASA/JPL/NIMA
This last topographic image colourfully displays the fault line 75 kilometres north of downtown LA. The whole segment of the fault line shown here last ruptured during the Fort Tejon earthquake of 1857. One of the largest recorded earthquakes in the US, it left an amazing 350 km surface rupture scar along the San Andreas. Were the Fort Tejon shock to occur today, the results could be catastrophic.
The beauty of these images belie the tremendously powerful and destructive force the San Andreas could unleash if it but slipped.
Source: environmentalgraffiti
Memorial Day Weekend is the third most perilous holiday for vehicular traffic behind Thanksgiving holds the number one spot, and the 4th of July. Here are some tips provided by Radarsign:
1. Don’t drive drowsy. According to the National Sleep Foundation’s Report on Drowsy Driving, 100,000 reported crashes, 71,000 injuries and 1,550 deaths every year are attributed to drivers falling asleep at the wheel. Add to that heavy holiday traffic and you have a recipe for disaster. If you are feeling drowsy, get off the road.
2. Wear your seat belt. The Department of Transportations (DOT) reports 50% of all vehicular deaths could have been prevented with seat belts.
3. Signal your intentions. Every move you make on the road impacts the decisions and actions of others. By signaling your intention to turn or change lanes, you ensure others are alert to your movements.
4. Do not tailgate. Leave a distance equal to one car’s length for every ten miles per hour. For example, if you are traveling fifty miles an hour, you should fall back a distance equal to five car lengths from the vehicle in front of you.
5. Move away from tailgaters. Many drivers attempt to “teach” a lesson to tailgaters by tapping their brakes telling the other driver to back off. Tailgaters typically exercise poor judgment and endanger themselves and others - especially when challenged. The best thing to do is move out of the way and let the tailgater safely pass you.
6. Avoid standing water. If you must drive through water, do so slowly and avoid sudden use of your brakes, turning too sharply or excessive acceleration. If you do hydroplane (an instance where the tread cannot channel the rainwater from under your tires), do not hit the brakes. Reduce your speed by taking your foot off the accelerator and turning the wheel in the direction you want to travel.
7. Know pedestrian rights. Always be aware of pedestrians at intersections and remember pedestrians have the right of way.
8. Turn on your headlights when visibility is low. The sobering statistic is that while only 25% of the miles we drive are at night, about 50% of the fatalities occur in the darkness-25,000 people each year.
9. Obey the speed limit. A difference of only five miles an hour can be the difference between life and death.
10. Stay alert. Talking on a cell phone, texting, reading maps - even listening to voice-directed GPS systems - can distract you from the road and lead to accidents.
