The Anthropocene and the Great Flood 1852-53 EarthCache
The Anthropocene and the Great Flood 1852-53
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Caution. The cache is NOT accessible at high tide.
The geological time scale is broken up into a series of periods, largely based on the types of fossils or major geological processes identified in the rock record. Our current Epoch is labeled the Holocene, which begins with the end of the last ice age, 10,000 to 11,000 years before present [YBP] depending on who you ask. The preceding age, the Pleistocene, included a series of ice ages with warmer intervals in between, which goes to about 1.8 million (M) YBP. The major time divisions that include the Epochs, and are called Eras. The major Eras include the Cenozoic (Present to 65M YBP; age of mammals); Mesozoic (65M YBP to 248M YBP; age of dinosaurs); Paleozoic (248M YBP to 543M YBP; period of "ancient' life. First fish, arthropods, amphibians, and retiles appear). Prior was the Paleozoic, in which either no fossils appear or only trace fossils of soft bodied organisms (such as a worm tube burrow).
Some geologist argue that in the last 100 years humans have had such a profound effect on the environment that a new Epoch should be identified, the Anthoropocene, the human Epoch. They argue this because of the way humans affect geologic process. Dams catch all the river sediment and deltas (think Louisiana) are starved of new deposits and erode and subside, large scale agriculture and mining dumps large amounts of sediments in other rivers fill river channels, levees prevent the deposition of new sediment in flood plains as soft sediments naturally compact or are oxidized (why New Orleans and the Sacramento delta are below sea level), etc..
The Martinez shoreline is an example of an arguably Anthropocene process. Early in the gold rush, miners used hydraulic mining to excavate entire mountain sides of Eocene auriforious* gravels dumping vast quantities of mine tailings into nearby rivers and streams. Sediments deposited in rivers don’t move every year, but large quantities are moved during period of major storms. In the winter of 1852-1853, A couple of major storms caused these hydraulic mining sediments to wash out of the Sierras and into the rivers and streams below. The Sacramento river channel was completely choked by these sediments resulting in flooding of most of the Sacramento Valley. Depending on the location, the San Francisco Bay became 1 to 3 feet shallower. And...from GZ (just north of the railroad tracks) to the current shoreline, open water was filled by sediments washed down from the Sierras. Later to make the land useable for development, additional fill what is not the park and facilities of the Martinez Shoreline Park.
Logging Requirements, send the CO the following:
1.In the subject line include the cache name and GC code.
2. You needn't record any information at GZ. However, GZ is not merely the entrance to the park. GZ is located at about the shoreline prior to the floods of the winter of 1852-53. All the land from approximately the railline to the current shoreline was accreated during these floods. Nothing needs to be recorded at GZ.
3.At Waypoint #1, small gravelly beach. Look at the gravels in this small beach. Do these gravels match the local rocks you can see from here in the nearby hillside? Is there any evidence of fill material? Not part of the logging requirement, but on the northeast corner of the footbridge note a really cool fossil rich sandstone block that was used as riprap.
4.At Waypoint #2, Look west. Look at the shoreline west of waypoint #2. What geological process is going on here? In recent decades the sediment loads from the hydraulic mining have largely been spent, and less is washing down stream. What is happening to the shoreline, is it progressing or receeding? If it is low tide step across the little gravelly beach. Pick out some soil out of the oppisite bank where there is no riprap. This is the soil deposited by the floods of 1852-1853. Compare the sediment from this bank to what material was present at the beach in Waypoint #1. What is the difference between these two materials?
*Eocene = Time period 34M to 55M YBP
**Auriferous = gold bearing
Geological Time Scale: (visit link)
1862 NY Times article on the floods in California: (visit link)
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