This is an Earthcache – as such, there is no physical cache. Instead after reading the lesson and examining the Kugel Ball at the posted coordinates, you will then answer 4 earth science questions and message me the answers. This earthcache is located on grounds of the Science Museum of Virginia with permission.

The Mary Morton Parsons Earth-Moon Sculpture, better known as the Grand Kugel, was installed here at the Science Museum of Richmond in 2003. A proportionately smaller moon was also installed and was placed 250 feet away from the earth (this moon was removed at the time of my visit). In 2004, the Grand Kugel was recognized by Guinness World Records as the world’s largest floating ball sculpture.

WHAT IS A KUGEL BALL? A kugel ball is comprised of a perfectly spherical stone ball that is set into a matching, perfectly concave cup. Water is then forced in from the bottom of the cup creating an evenly distributed, incredibly thin layer of water. The ball, no matter how heavy, can then be moved on the liquid surface as though it weighed nothing at all. The jet of water underneath this kugel revolves the earth every 56 seconds.

When it was first installed, the original 29 Ton kugel ball was sculpted originally from gabbro, which is commercially sold internationally as South African Black Granite. Gabbro is made up of mostly dark minerals like pyrite, chalcopyrite, and magnetite. It is coarse-grained igneous rock that forms when magma cools slowly deep within the Earth.

In 2004 a small crack appeared along the equator. Over the next year the crack eventually grew to encircle the entire 9-foot-wide globe. This prompted the museum to stop its motion and replace it with this current ball in 2005. At some point the original Kugel Ball was moved inside the museums grounds where it can still be visited, but it no longer rotates on water. I was able to see it in 2022 with my family (see photo below).

The crack’s exact cause remains unknown, but temperature stresses may have contributed. Although granites are extremely durable, but they aren't indestructible. Prolonged exposure to harsh sunlight, especially an outdoor application like this one here in Richmond, may contribute to a subtle changes and cracks in appearance over an extended period.

You see, granite is especially good at holding heat. These stones can reach temperatures more than 40 degrees higher than the surrounding air on a sunny day, and the darker the stone, the hotter it gets. Stone expands when it gets hot, and contracts as it gets cold. If the temperature changes rapidly in either way, cracking can occur. Knowing that granite comes from molten magma that’s 1,000 to 2,000 degrees Fahrenheit you would think that it is resistant to being out in the sun. There are four ways that heat can damage even the toughest granites:

1. The minerals can undergo physical changes, meaning the heat can make stone redder, yellower, darker, or lighter.
2. The stone can become more porous. As the stone heats up, the tiny spaces in between each grain can start to expand, forming microscopic cracks and cretae a rougher uneven surface.
3. Sealant can react to the heat, such as when you put a hot pan on a granite countertop and it leaves a mark.
4. The granite can crack.

The current Grand Kugel is carved from a stronger lighter-colored French Tarn Granite, which now matches the granite used in the original base. This highly polished gray granite is expected to absorb less heat from the sun as well as reflect the sunlight, which will reduce thermal stress to the stone. The main three minerals that make up this rock are Quartz, Mica, and Plagioclase Feldspar.

Tarn Grey granite is a Commercial name for a medium to coarse-grained, grey to nearly white granite of the Carboniferous period, a geologic period that lasted about 60 million years (from about 358.9 million to 298.9 million years ago). It is a durable and extremely strong granite with a low porosity, which makes it perfect for using it for in outdoor environements.

LOGGING REQUIREMENTS:

To log this Earthcache: Read the geology lesson above. Answer all four questions posted below. Answers can be sent via e-mail or messenger contacts on my Geocaching profile within a reasonable time. Group answers are fine, but do not post the answers to the questions in your logs.

QUESTION 1. Why did the original black kugel ball crack?

QUESTION 2. Now look closely at the crystals that make up this Tarn Granite. Would you say the range of Plagioclase Feldspar in this stone is:
A) 75% to 100% Mostly whitish Plagioclase Feldspar with barely any minerals showing.
B) 50% to 75% A more even "salt & pepper" mixture of Plagioclase Feldspar and Quartz.
C) 0% to 50% Rock is a majority of other darker Minerals and with less amounts of Plagioclase Feldspar and Quartz.

QUESTION 3. How do you think this mineral distribution helps this Kugel Ball stay cool?

QUESTION 4. How does the temperature from this darker granite bench feel compared to the Tarn granite base cup of the Grand Kugel?

OPTIONAL PHOTO: Posting a photo that readily indicates that you (and anyone else logging the find) are at the location.

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REFERENCES:
1. Whole new world arrives at museum, A.J.Hostetler, Richmond Times-Dispatch, page A4, October 9, 2005, Newspaper, newspapers.com
2. Global warning: Big kugel is cracked, A.J.Hostetler, Richmond Times-Dispatch, page B1, November 10, 2004, Newspaper, newspapers.com
3. Museum Has a new Grand Kugel, J.Caggiano, The News-Virginian, October 13, 2005, Page 2, Newspaper, newspapers.com
4. Round and Tall, Earthcache by Rainbowtree, 17.Sep.2021, website, geocaching.com
5. Hot Stuff: High Heat Can Damage Natural Stone, K.Kirk, Slippery Rock Gazzette, website, slipperyrockgazette.net