High Desert Geology: Mojave River EarthCache

High Desert Geology

-Mojave River-

The High Desert's First Earthcache and My 100th Cache Hide

The Mojave River is the largest drainage system in the Mojave Desert.

It has been nicknamed the "Upside-Down and Backwards" river. "Upside-

Down" because the water flows primarily underground. "Backwards" because

the water flows North, away from the Ocean, instead of South towards the

Ocean as most rivers do.

The Mojave River currently flows North due to Geological events. The Mojave

River system began developing as Westward-Flowing streams were blocked

by the uplift of the Transverse Ranges along the greater San Andreas Fault.

The Transverse Ranges, the local San Bernardino Mountains, represent a

complex of tectonic forces stemming from the interaction of the Pacific Plate

and the North American Plate along the San Andreas Fault System. As

Tectonic forces drove the Pacific Plate under the North American Plate, the

North American Plate lifted upward creating the Transverse Ranges and a

northern slope that redirected water runoff away from the Ocean and North to

the Desert. With the San Andreas fault pushing the mountains up, slowing

general drainage of the area, the Victorville Basin became a marshland for

many years before the Mojave River reversed direction inland.

Chronology of the Ancestral Mojave River

11 - 10 million years ago:   The region sloped toward the Pacific Ocean

8 - 7.6 million years ago:   Birth of ancestral Transverse Ranges (San  Gabriel fault)

3.5 million years ago:   San Gabriel Mountains rise blocking the slope to the

ocean and forming marshlands. Ancestral Deep Creek coming out of the

San  Bernardino Range begins to appear.

2.5 - 2 million years ago:   Continued rise of the San Bernardino Range

along the San Andreas fault reverse the regional drainage direction.

1.5 - 1 million years ago:   The development of faults further to the north  and east.

500 thousand years ago:   Appearance of perennial lakes Harper and Manix

70 - 80 thousand years ago:   Ancestral Mojave River develops as an  incised channel with a course.

The Mojave River originates in the Upper Watershed of the San Bernardino

Mountains. This area comprises less than 5% of the total drainage basin area

yet it accounts for more than 95% of the total basin precipitation. Its

ephemeral waters, or episodic-lasting a short duration, gather from north of

the mountains ridgeline and flow down a series of creeks and washes. The

Mojave River's source is in the Eastern San Bernardino Mountains, one of the

Transverse Ranges, above Hesperia / San Bernardino. The West Fork of the

Mojave River flows from Lake Silverwood, formed by Cedar Springs Dam,

which overflows in to the Mojave River Forks Reserve area. The East Fork of

the Mojave River flows from Deep Creek. The East and West Forks join

together at the Mojave River Confluence at the Mojave River Dam

(Deep  Creek Spillway).

Mojave River Western Region

  Downstream of the Deep Creek Dam, the Mojave River flows North and East,

underground in most places, through Hesperia, Victorville, Apple Valley, and

Barstow. The Mojave River does come above ground in certain areas where

impermeable formations of rock forces water above ground. Usually, the river

flow can be seen at the Upper Narrows between Victorville and Apple Valley,

then downstream past Barstow at the Lower Narrows as the river begins its

way through Afton Canyon. The river winds down the canyon and seeps back

into the sand disappearing before it reaches Soda Lake near Baker.

Mojave River Central Region
 

The Mojave River ends at the Mojave River Wash at the western edge of

Mojave National Preserve. During heavy flows, the river reaches Soda Lake,

near Baker and has reached Silver Lake in historic times.  At the

Mojave River’s peak during this last ice age, Lake Manix and Lake  Mojave were large

inland lakes. Dry Troy Lake and Coyote Lake are modern  remnants of Lake Manix

while Dry Silver Lake and Soda Lake are remnants of  Lake Mojave. “The development

of these lakes and other lakes in the region  were progressive over time, with Manix Lake

filling first, and Mojave Lake  forming later when the Lake Manix filled to capacity

and spilled westward,  ultimately carving Afton Canyon during the last glacial

maximum about  18,000 years ago” (Jefferson, 2003).


Mojave River Eastern Region

Mojave River Historical Notes

The Serrano Native Americans lived along the river for up to 8,000 years. The

Indian trail, later the immigrants' Mojave Road, paralleled the river from Soda

Lake to the Cajon Pass. Native Americans used this trade route where water

could easily be found in route to the coast. Later, the Old Spanish Trail and

Salt Lake Trail (Mormon Trail) joined up with the river and Mojave Road near

the present-day location of Daggett.

Mojave River Lakes

Harper Lake : Harper Lake is the furthest upstream and possibly the oldest

lake of the Mojave River appearing 500,000 years ago.

Lake Manix : Lake Manix was the largest lake of the Mojave River system. It

is said to have existed as far back as 470,000 years ago. Approximately

14,000 years ago, at a high water mark, it is thought that a seismic event

caused a breach in the basin’s shoreline which began the formation of Afton

Canyon.

Troy Lake : Troy Lake is a remnant lake of Lake Manix. Some theorize that

Troy Lake is an overflow point for the headwaters of the watershed flowing to

Bristol Lake, then through a series of lakes to the Colorado River. Although

No evidence of this possibility has been found to support this theory.

Coyote Lake : Coyote Lake may have also been a remnant lake of Lake

Manix. It may have had flow directly in from the Mojave River at one time.

Afton Canyon : Two general theories may explain the formation of Afton

Canyon. The first states that during a time of high water levels, the water

poured over the top of the lakeshore and into the Lake Mojave basin to the

east. This started a period of erosion several hundred to several thousand

years long. The second theory is that a seismic event occurred which

breached the canyon wall and lead to a rapid period of draining, possibly

emptying Lake Manix in only a few days or weeks.

Mojave River Fan : The Mojave River Fan is a clastic wedge, possibly

deposited during the initial carving of Afton Cayon.

Cronese Basin : In the past, the Mojave River fan may have diverted flow

from the Mojave River into the Cronese lakes during periods of  flooding.

Lake Mojave : Part of the Kelso Wash, consisting of the Soda Lake and Silver Lake

Logging Requirements:

You Must Visit Two locations along the Mojave River and Email the Required information.

Location 1: Visit the Listed Coordinates to this EarthCache.

Location 2: Visit any one of the 13 Waypoint locations given along the Mojave River.

(You Do Not have to Visit the Exact Waypoint Coordinate Location, Nearby is sufficient)

Email me a thorough description of the Two Locations that you Visited along with

the answers to the following questions.

Optional Requirements: Strongly Recommended

Post a picture of yourself at the listed Coordinates with the Mojave River Confluence area in the Background as well as a second picture of yourself at your second location. Sharing these pics will allow myself and other Cachers to enjoy in your experience.

Thanks and Enjoy
-RHINO-


Sources:
USGS, US Department of the Interior
USGS Western Region Geology and Geophysics Science Center
Digital Desert