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To Log This EarthCache include:
1. The name of this EarthCache on the first line of your email.
2. The number of people in your group.
3. Calculate the value of the gold block found at Carson Hill in 1854 in today's market.
4. Which Big Ideas (1-9) are connected (list)?
5. Which GeoPrinciples (1-7) are relevant (list)?
6. Include a photo or 2 if you're so inclined (optional).
Note: In order to manage email volume, you may assume your responses are accurate if you do not get an email after logging this EarthCache. If a response is grossly inaccurate, you will not receive credit for the cache.
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GEOLOGY OF CARSON HILL
The main mass of rock in the Sierra Nevada is a huge batholith of granodiorite that intruded into, and metamorphosed, sedimentary and volcanic rocks of Paleozoic and Mesozoic age. The metamorphic rocks are found in the western third of the range, generally in the foothills. They are part of a large fold and thrust fault belt, similar to what is forming in northern California today along the north coast in Humboldt and Del Norte counties. Carson Hill is cut by multiple fault strands of the Melones Fault Zone. Rock units include the Calaveras Complex with hornfels, limestones and marbles, phyllites, quartzites, schists, and slates. The Don Pedro terrane units include metasedimentary and metavolcanic rocks, as well as amphibolites, greenstones, quartzites, phyllites, schists, serpentinite, and slates. There are also dioritic aplitic dikes that cross cut through the metamorphic rocks.
Approximately $26,000,000 worth of gold was reported mined from Carson Hill by 1962 (see Figure 1). At 2017 prices ($1228/oz.) that would equate to approximately $900,000,000. The mine has been the largest producer of lode gold in the country. The town of Melones on the southern side of Carson Hill (now under the water of New Melones Reservoir) was the largest mining camp in the state at one time, with a population estimated between 3,000 and 5,000. People “came in crowds to see the mine”.
Figure 1: Image of the entrance to the modern day Carson Hill Mine, currently marketing aggregate products.
The largest piece of gold to come out of the Mother Lode apparently was discovered here at the Morgan Mine (see Figure 2), in November 1854, weighing 195 Troy pounds and was valued at the time to be $43,534.
Figure 2: Image showing the Morgan Hill Mine, 1920.
The following is from the Calaveras Heritage Council archives:
“On November 22, 1854, the largest mass of gold ever found in the United States, the “Calaveras Nugget,” was taken from the Comstock claim on Carson Hill by four Americans and one Swiss miner. It weighed 195 pounds troy and was valued at $43,534. It was purchased by a man from New Orleans, exhibited at the French Exhibition in Paris in 1856, and apparently melted down shortly thereafter (Costello 1983:13).”
To complete this EarthCache, calculate the current value for that piece of gold, assuming gold is currently $1,228/Troy ounce (as of May 12, 2017) $4,595.25/Troy ounce (as of January 16, 2026).
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EARTH SCIENCE BIG IDEAS
The Earth Science education community put together 9 “Big Ideas” for the Earth Science Literacy Initiative (ESLI), shown below. Their purpose was to highlight the main concepts and ideas a person should understand to be literate in the earth sciences:
An Earth-science-literate person:
• understands the fundamental concepts of Earth’s many systems
• knows how to find and assess scientifically credible information about Earth
• communicates about Earth science in a meaningful way
• is able to make informed and responsible decisions regarding Earth and its resources
Which of these Big Ideas below do you think are most relevant to this EarthCache?
Earth Science Literacy Project:
1. Big Idea 1: Earth scientists use repeatable observations and testable ideas to understand and explain our planet.
2. Big Idea 2: Earth is 4.6 billion years old.
3. Big Idea 3: Earth is a complex system of interacting rock, water, air, and life.
4. Big Idea 4: Earth is continuously changing.
5. Big Idea 5: Earth is the water planet.
6. Big Idea 6: Life evolves on a dynamic Earth and continuously modifies Earth.
7. Big Idea 7: Humans depend on Earth for resources.
8. Big Idea 8: Natural Hazards pose risks to humans.
9. Big Idea 9: Humans significantly alter the Earth.
For more details see: Earth Science Literacy Initiative
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GEOPRINCIPLES
There are several fundamental principles, developed over time, that guide geological reasoning and critical thinking, listed below. Read each short description, then use your best judgement to determine which principle, or principles, best relate to this EarthCache.
7 Principles in Geology:
1. Superposition – the oldest strata are at the bottom of the sequence
2. Original Horizontality - layers of sediment are originally deposited horizontally
3. Lateral Continuity - layers of sediment initially extend laterally in all directions
4. Faunal Succession - fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances
5. Law of Intrusive Relationships - the geologic feature which cuts another is the younger of the two features
6. Uniformitarianism - the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe
7. Catastrophism - the theory that the Earth has been affected in the past by sudden, short-lived, violent events, possibly worldwide in scope
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LOGISTICS AND SAFETY:
Park next to the historical monuments. Please be aware of any truck (or other) traffic traveling in and out of the Carson Hill mine.
Visitors to this site should plan ahead and prepare by:
• Knowing the regulations and special concerns for the area you are planning to visit (obeying laws that prohibit collection or destruction of artifacts);
• Carrying a map and a GPS unit and/or compass;
• Staying on existing roads and trails;
• Staying away from any/all mine shafts and adits;
• Planning for extreme weather, hazards, and emergencies;
• Being aware that cell phones DO NOT usually work in the rural areas away from the major highways;
• Leaving your travel plans with a responsible party, including the date and time of your return;
• Being aware of any natural hazards associated with the region (e.g. poison oak, rattlesnakes, mosquitoes, cliffs/steep slopes, etc., etc);
• Carrying a full-size spare tire, extra food, water, and warm clothing;
• Following the “Tread Lightly" and "Leave No Trace” philosophy.
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To Log This EarthCache include:
1. The name of this EarthCache on the first line of your email.
2. The number of people in your group.
3. Calculate the value of the gold block found at Carson Hill in 1854 in today's market.
4. Which Big Ideas (1-9) are connected (list)?
5. Which GeoPrinciples (1-7) are relevant (list)?
6. Include a photo or 2 if you're so inclined (optional).
Note: In order to manage email volume, you may assume your responses are accurate if you do not get an email after logging this EarthCache. If a response is grossly inaccurate, you will not receive credit for the cache.
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Note: For a brief summary of the geologic history of the Central Sierra, see this EarthCache:
Dragoon Gulch EarthCache
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REFERENCES:
1. Busby, Cathy J., Andrews, G.D.M., Koerner, A.K., Brown, S.R., Melosh, B.L., and Hagan, J.C., “Progressive derangement of ancient (Mesozoic) east-west Nevadaplano paleochannels into modern (Miocene–Holocene) north-northwest trends in the Walker Lane Belt, central Sierra Nevada”, Geosphere 12, p. 135-175, 2016, http://www.geosphere.gsapubs.org.
2. Busby, Cathy J., Koerner, Alice, Hagan, Jeanette, and Andrews, Graham, 2012, “Sierra Crest graben: a Miocene Walker Lane Pull-apart in the Ancestral Cascades Arc at Sonora Pass”, in, N. Hughes and Garry Hayes (eds), “Geological Excursions, Sonora Pass Region of the Sierra Nevada”, Far Western Section, National Association of Geoscience Teachers field guide, p. 8-36.
3. Calaveras Heritage Council, study from report: Costello, Julia G. and Judith Marvin (Cunningham), Archaeological and Historical Study of Carson Hill, Calaveras County, by Foothill Resource Associates, for Carson Hill Gold Mining Corporation, Altaville, www.calaverashistory.org, 1985.
4. Earth Science Literacy Initiative (ESLI), 2010, http://www.earthscienceliteracy.org/.
5. Konigsmark, Ted, 2003, “Geologic Trips: Sierra Nevada”, GeoPress.
6. Portland State University, “Glaciers of California”, last updated 08-04-2011, http://glaciers.research.pdx.edu/glaciers-california.
7. Putnam, Roger, (pers. comm.), May 2017, Professor of Earth Science, 11600 Columbia College Drive, Sonora, CA, 95370.
8. Schweickert, Richard, 2006, “Accretionary Tectonics of the Southern Part of the Western Sierra Nevada Metamorphic Belt” (modified from a 1999 guidebook article by Schweickert, Girty, and Hanson), in J. Tolhurst (ed), “Geology of the Central Sierra”, National Association of Geoscience Teachers Far Western Section Fall Conference field guide, p. 55-95.
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