Antioch Dunes EarthCache
Hidden : 8/6/2013
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:


Some warnings first.
>What out for traffic both when out of your car and when pulling in and out. Particallarly along Wilbur Avenue, the road conditions are not ideal.
>Although it is only about 1 mile from GZ to waypoint 1 and on to waypoint 2, because of the narrow road and high speed traffic, I strongly recommend not traveling on foot or by bike. Car caching is recommended
>Do not enter private property. There is absolutely no reason to so as to log this cache.
>For disabled cachers, if you let me know you will not need to exit your vehicle at waypoint 2 and I'll give full credit, hence the one star terrain rating.
>Regarding ADA accessability, you do not need to leave your vehicle at GZ and waypoint 1. At waypoint 2, if you are less abled, let me know in your response email and I'll accept your log

Predevelopment the Antioch Dunes covered area from about the current Antioch Dunes Preserve (you'll get there in the end) east to Oakley and northern Brentwood area. These aeolian (wind blown) deposits are believed to have formed during the later portion of the most recent ice age, forming roughly 40,000 to 10,000 years before present. The Pleistocene geological, roughly 1 million to 10,000 years before present, included a series of protracted ice ages with short interglacial periods with climates similar to present. During the ice ages large volumes of water were tied up in ice sheets covering the northern and southern poles. These ice sheets extended as far south as northern Washington state and central New England. The lakes of Minnesota and Wisconsin, the great lakes, and the finger lakes of upstate New York and New England were all gouged out by these ice sheets. Cape Cod and Long Island (New York) are terminal moraines (dirt and rock piles pushed out by glaciers).

Because so much water was tied up in ice, sea level was approximately 300 feet lower than present. The Farallon Islands now 40 miles off shore were then connected to the mainland, what is now the Golden Gate, Carquinez Straits, and Delta were deeply carved river valleys. With the ups and downs of sea level during interglacial periods and ice ages (respectively), sands were deposited in these river valleys when flooded, and then blow inland with the prevailing winds when exposed. If you've spent any time in Antioch during the summer, you've experienced those prevailing, inland winds.

At GZ your area at the intersection of Eighteenth Street and Viera Street. Pull over. Look down Viera to the north. You'll see the road undulating with the original ground surface. Many of the surrounding areas have been leveled to eliminate the original ground topography, but not along Viera. Observe young grasshopper, question one to log this cache is observed as you drive down Viera.

STOP at waypoint 1. No need to enter private property. On the relative scale of permeability, wind-blown sand is pretty high. In most areas of sand dunes streams do not form even during the largest rainfall events. The soils are so permeable that the water infiltrates before there can be any runoff. At this waypoint you'll see a small stormwater control structure. Observe this for question 2.

Finally your at waypoint 2, the final stop. Carefully pull in to the driveway entrance to the Antioch Dunes preserve just to get off the main roadway. You will stay on the public right of way and not enter the closed preserve. This is one of two units of the preserve. These are the last two remaining undeveloped postage stamps sized parcels of the Antioch Dunes terrain that use to cover easily more than 100 square miles. The unit soils and evolutionary history of this area is habitat for several plant and insect species that now cling to the edge of extinction. The endangered Naked-Stem Buckwheat is the sole host to the Lange's Metalmark Butterfly; both only found in the preserve and a few adjacent parcels. Just to the left (west) of the gate is a small patch of the native soil of this preserve. Examine the soil to answer the final questions.

To log this EC mail answers to the following questions and email them to the cache owner:

1) Describe the topography of Viera Road and the surrounding terrain (to the railroad tracks). What is the relative elevation between the highs and lows.

2) At way point 2, what kind of stormwater structure is here? Is there an outlet? What does this tell you about the permeability of the soils?

3) At way point 3, the entrance to Antioch Dunes preserve, describe the texture of the soil you observe. This soil is very typical example of wind-blown deposits. Are the grains of relatively similar size? What is the average diameter (guess)? A grain of rice is about 1 millimeter thick, use that for comparison.

UC Berkeley. "Lange's Metalmark Butterfly (Lepidoptera: Riodinidae)" [website] (visit link)

USFWS. 2001. "Antioch Dunes National Wildlife Refuge. Draft Comprehensive Conservation Plan". U.S. Fish & Wildlife Service.

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