Welcome to the Alaska State Capitol Building, the seat of power for the largest state in the union*! Note that as this is an earthcache there is no container to be found at the posted coordinates. In order to log this cache as "found" you must send the cache owner answers to the logging requirements at the end of the description. This is most easily completed with the message center feature. If you have any questions or concerns, please reach out to me! As you gather your answers to the questions for this earthcache, please take care to stay on the public sidewalk. There is no need to enter the Capitol Building to answer the questions.
*In terms of landmass
Background
The Alaska State Capitol Building was originally conceived in 1929, more than 30 years before statehood, as a place for federal employees to work. Although partially funded by congress, the citizens of the fledgling territorial capitol bought and donated the land on which the building sits to finalize the project. Construction was completed in early 1931 and the building was dedicated later that year.
In 1959 when Alaska achieved its statehood, the building was converted from the federal building to the State Capitol. As early as 1960 there have been a multitude of attempts to move the capitol from its seat in Juneau to the Anchorage area. All have failed.
As you complete this Earthcache you will need to examine two different sections of the Capitol Building: the columns and the facade. As you complete this Earthcache you will be ask to make comparisons between the two, and ultimately identify the building material based on the composition.
Limestone
Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris. The limestone included in the Capitol Building was quarried from the Salem Formation and is commonly referred to as "Indiana Limestone" due to most of the quarries being located in that state Indiana Limestone was formed during the middle to late Mississippian (335-340 million years ago), when most of what is now the USA was covered by shallow seas that straddled the equator.
The Salem Formation crops out along a thin, irregular band in south-central Indiana. Most quarries lie between the cities of Bloomington and Bedford.
Quarrying of Indiana Limestone began in 1827 with the opening of the Richard Gilbert Quarry. By 1900, Indiana limestone represented 1/3 of the total domestic limestone industry, and increased to 80% by 1920.
The limestone is soft and easily worked when quarried, but once the quarried rock dries it becomes case-hardened, that is, its surface becomes harder and more resistant to weathering. Indiana Limestone is a freestone, which means that it has no preferential direction of splitting. It can be planed, turned on a lathe, sawed, and hand worked, making it highly versatile.
Where quarried, the Salem Formation varies from 8 to 18 meters (25 to 60 feet) in thickness, and is unusually massive (i.e., lacks partings and stylolites). For a rock, the Indiana Limestone is chemically pure and consistent, being composed of >97% calcite. The combination of these physical and chemical characteristics make the Indiana Limestone well-suited to building because it is more durable than a typical limestone, it can be cut into very large blocks, and it can hold fine detail when carved.
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite and dolomite. The marble used in the Capitol Building was mined from Prince of Wales Island in Southeast Alaska in the early 1900s. Marble is commonly used in buildings and sculptures due to its hardness and visually appealing brilliance.
Geologically, marble is specifically formed during the metamorphosis of limestone. When it is formed from a limestone with very few impurities, it will be white in color. Marble that is composed of limestone and another mineral (often referred to as an impurity) will cause pigmented veining in the marble. The specific impurity will often cause the marble to have a different hue: olivine can cause green tints, sulfur and clay can cause grey and brown tints, and ocher can cause red tints. "Marble" that is predominantly black, orange, or another color other than white, is actually a manufactured man-made granite and not considered to be a "real" marble.
Under the conditions of metamorphism, the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. Most marble forms at convergent plate boundaries where large areas of Earth's crust are exposed to
regional metamorphism. Some marble also forms by contact metamorphism when a hot magma body heats adjacent limestone or dolostone. During metamorphism, the calcite recrystallizes and the texture of the rock changes. In the early stages of the limestone-to-marble transformation, the calcite crystals in the rock are very small. In a freshly-broken hand specimen, they might only be recognized as a sugary sparkle of light reflecting from their tiny cleavage faces when the rock is played in the light.
As metamorphism progresses, the crystals grow larger and become easily recognizable as interlocking crystals of calcite. Recrystallization obscures the original fossils and sedimentary structures of the limestone. Recrystallization is what marks the separation between limestone and marble. Recrystalization will give the previous porous and dull limestone a brilliant shimmering and "polished" look.
Logging Tasks
Please answer the following questions, to your best ability, using the information above and your observations at the posted coordinates. Any "Found It" logs that fail to submit the answers to the CO in a timely manner are subject to deletion. I will attempt to reach you to resolve any discrepancies prior to taking this course of action.
- Look at the columns and the facade on the front of the capitol building. Which is limestone and which is marble? What indicators give it away?
- Look at the marble. What is the predominant color. Is this a "real" marble or man-made?
- What tint is the marble? What impurity likely caused the coloration?
- Compare the limestone facade with the marble. Which contains a higher purity of calcium carbonate? How did you determine this?
- (Optional) Include a photo of yourself in your log but please do NOT show either the columns or the facade.
Sources
- http://www.sitnews.us/JuneAllen/AKCapitol/102004_alaska_capitol.html
- http://geologywriter.com/tag/alaska-marble/
- http://stonecutter.blogspot.com/2014/02/the-alaska-marble-story.html
- https://www.gmswerks.com/blog/article/identifying-marble
- Powell, Wayne G. “Indiana Limestone.” Academic Brooklyn, CUNY, 2004, academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCbuilding/IndianaLimestone/IndianaLimestone.htm.