Mormon Rocks and North Etiwanda Preserve

Bruce ButterfieldGeography 111Thursday 1pm

Mormon Rocks

Mormon Rocks was formed by folding along the San Andreas Fault between the North American and the Pacific Plates. Mormon Rocks is a tilted fault block.

Mormon Rocks

Mormon RocksMormon Rocks was named after a band of

Mormon settlers from Salt Lake City, led by Amasa Lymand and Charles Rich, who passed through the Cajon Pass in 1851 on their way to San Bernardino. This was because it was smoother than the Mojave Indian Trail.

San Andreas Rift Zone

Rift Zone

The San Andreas Fault is 400 hundred miles and runs from San Francisco to the Salton Sea in the Imperial Valley. The San Andreas Fault is a strike

slip/transform fault. In this picture the rift zone is what separates the North American Plate(East) and the Pacific Plate(West).

Granular Structure of Mormon Rocks

Mormon Rocks is composed of sedimentary rock. They would be classified as a conglomerate. Conglomerate is composed of rounded gravel. Mormon Rocks are cemented deposits of sandstone.

Gravel

Pockmarks

Pockmarks

The holes(pockmarks) in Mormon Rocks are caused by the expanding and contracting of the rocks because of temperature. When the rocks expand and contract the little pieces of rock/gravel fall out. After the rocks fall out, water and wind erode the holes to make them bigger.

Three Tiers of Vegetation Mormon Rocks

Scrub OakShrubGrass

1. Top Tier-Scrub Oak

2. Middle Tier-Shrub

3. Bottom Tier-Grass

The North Etiwanda Preserve is vital because the Riversidian Alluvial Fan Sage Scrub (RAFSS) habitat is extremely rare and this is one of the only places it is still intact. The RAFSS runs along the southern base of the Transverse mountain ranges. It is a distinct and rare plant community. The vegetation is adapted for periodic flooding and erosion and usually found on alluvial fans. It covers the gently slopping alluvial fan surfaces that have not been recently flooded.

On the western boundary there Day Creek is channelized. This eliminates the depositional processes that build alluvial fans over time. Absence of flooding can lead to more mature upland forms of alluvial scrub and alluvial chaparral vegetation. However, no flood controls within the park which keeps the vegetation intact.

Flood ControlDrinking Water

Early ranchers had to be creative getting water for agriculture and consumption into the area. Signs of this are still present in the preserve. There are long segments of clay pipes all over the place. There were also

stone walls built to support the pipes.

Stone wall

Clay pipes

California Brittlebrush

Sycamore Tree

Yucca

White Sage

Alluvial Sage Scrub Habitat

The North Etiwanda Preserve has 473 acres of alluvial shrub. It is characterized by shrub-dominated plant

communities. One such type is white sage. There are 120 acres of Chamise Chaparral and 92 acres of alluvial

chaparral. The California Brittlebrush grows in sage scrub. Sycamore trees are found in Sycamore Alluvial

Woodland.

There are multiple endangered species within the preserve. The California Gnatcatcher is an

endangered bird found here. The San Bernardino Merriam Kangaroo Rat is also with the North

Etiwanda Preserve. Other species include the San Bernardino Ringneck Snake, American Badger, and

Southern Sagebrush Lizard

Gran Prix Fire

Burnt Tree

Burnt Wood

The wildfire in 2003 burnt almost the entire vegetation in the Etiwanda Fan. Fortunately, fire is a common and natural occurrence in Southern California and the biological community responded with resilience afterwards. The vegetation is able to recover using both crown sprouting and seed germination. Recovery begins almost immediately and the vegetation can usually return to a pre fire state.

Smog

Suburban Sprawl

This is the view looking back towards Fontana/San Bernardino from the North Etiwanda Preserve. While the preserve is beautiful, the ever present dangers of pollution and

development are looming. This suburban development is what makes the preserve so vital.