Friday, 4 January 2008

"Down Mexico Way"

This has got to be one of the most geographically interesting camp sites of Mark's journey! (Remember that although the GPS is showing 4am this morning, this represents sundown on the 3rd for Mark). We will come back to the campsite later......

The route which brought Mark to this point is also full of geographical interest..After leaving San Diego, the Inter State 8 climbs up through the Laguna Mountains (referred to in yesterday's posting) to a height of around 2000m. Part of today's journey through the mountains took Mark through the Cleveland National Forest, the most southerly national forest in the USA. According to the forest website "The Cleveland National Forest is a very special place in southern California. The forest is a haven for wildlife and plants. The wild shrub and tree-covered mountains are remnants of a landscape that at one time covered most of southern California. With the settling of missions, towns, cities, and suburbs, populated areas now surround the mountains. Natural areas for plants and animals have become smaller and smaller, and in some cases, have disappeared." Mark may have seen evidence of severe wildfires (associated with the Santa Ana winds described in this posting )which frequently sweep the area - some as recently as last year. The Cleveland forest was also the location of the Cedar Fire, the largest wildfire in California history which devastated 720 sq miles of the forest in 2003. A good general impression of the scenery of the Laguna Mountains can be gleaned from the image above and from the following borrowed from the Panoramio layer in Google Earth. Mark will certainly have cycled across this viaduct at some point yesterday.Climatically, the mountains to the east of San Diego are hugely significant as they act as a barrier to the inland penetration of oceanic influences. Any moisture which on-shore winds may bring to the south of California is trapped to the west of the mountains. This, added to the fact that the prevailing winds in this region are north easterlies (and hence dry as they are coming from the heart of the continent) means that there is desert to the east of the mountains.

The altitude of the mountains does have its benefits, however, as I spotted when I looked more closely at this strange pattern which was visible from the air. This is a 2 mile line of 25 wind turbines (and their shadows!)

Some investigation reveals them to be the Tecate Divide wind farm with the largest capacity wind turbines in the USA. They also represent the first large-scale commercial wind farm on Indian lands in the US. The tribe will collect fees on a 20-year lease, plus royalties from electricity sales to San Diego Gas & Electric.

Travelling east and descending from the mountains, Mark would have passed within a couple of kms of the heavily protected Mexican border and into the very arid environment of the Colorado desert to the east (shown below within the dotted yellow line). ... which, understandably is very sparsely populated except where there has been reason to settle as here in the enigmatically titled 'Plaster City'
...whose sole reason for being is a large gypsum quarry...
The last part of yesterday's route took Mark across the Imperial valley - the striking area of irrigated and intensively farmed land which lies south of the Salton sea in the Colorado desert. Considering that this area receives less than 75mm of rain per annum (desert dry is anything less than 250mm), cultivation in the Imperial valley is all the more amazing. The intensive and highly productive farming is entirely based on irrigation which come from the All American Canal dug from the Colorado river in the 1930s and early 40s. It is the largest irrigation canal in the world. The Salton Sea occupies a point over 200m below sea level and only came into being as the result of a man-made environmental disaster that occurred between 1905 and 1907 , when improper management of irrigation routes from the Colorado River caused the river to flow unchecked into the Salton Sink for some two years. Today, its presence is largely maintained by agricultural and irrigation run-off. It is highly saline and polluted with agricultural chemicals. There was an interesting article in National Geographic about the Salton Sea and its environs which you can read here.

Mark's route yesterday took him across the 30km wide expanse of irrigated land, through the town of El Centro which lies at its heart...
...which brings us back to where we started ..
....where an irrigation canal marks the edge of the desert and the difference between desert and productive farmed land can be measured in just a few metres!

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