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December 16, 2012

Geology Word of the Week: G is for Glacial Erratic

Me, standing on top of an erratic boulder in Nome, Alaska, Summer 2012. Picture courtesy of Urban Burger.

def. Glacial Erratic: A rock which has been transported and deposited by a glacier and which has a different lithology than the rock upon which it has been deposited.¬†Often, erratic rocks have an angular shape because they were broken off of bedrock by glaciers and have not yet had time to be weathered and rounded by water, wind, and other erosional forces. Glacial erratics can range in size from very …

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December 9, 2012

Geology Word of the Week: F is for Float

A cairn built out of float rocks in Wyoming, Summer 2011.

def. Float: Loose pieces of rock that are not connected to an outcrop. If you’re in the field with a geologist, you’re very likely to hear the word “outcrop” and the phrase “in situ“. When describing, identifying, mapping, and understanding rocks, geologists like to see rocks in context. If rocks were alive, you might say that geologists like to observe rocks in their natural habitats. You might say that geologists …

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December 2, 2012

Geology Word of the Week: E is for Eurypterid

Geology Word of the Week: E is for Eurypterid

def. Eurypterid: 1. A group of extinct arthropods¬†that were fearsome marine predators of the Paleozoic. There were over 200 different species of eurypterid, and they ranged from very small (less than 20 cm) to very large (greater than 8 feet). Because of their long tail, eurypterids are sometimes called “sea scorpions.” Indeed, they are closely related to today’s scorpions and other arachnids. One species of eurypterid, Eurypterus remipes, is the …

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November 23, 2012

Geology Word of the Week: D is for Drumlin

Geologist Liz Johnson in front of drumlins in Clew Bay, Ireland. Picture courtesy of Liz Johnson.

def. Drumlin: An elongated hill or ridge with a shape resembling an upside-down spoon or a half-buried egg that was formed out of glacial till– and sometimes other material such as gravel and even bedrock– that was shaped by the movement of a glacier. A drumlin carved in bedrock is usually called a “rock drumlin.” Drumlins have a steeper end and a less-steep, more tapered end. The shape of a …

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November 18, 2012

Geology Word of the Week: C is for Columnar Jointing

Columnar Jointing diagram.

def. Columnar Jointing: A structure that forms in rocks (most commonly in basalt) that consists of columns (mostly commonly hexagonal in shape) that are separated by joints or fractures in the rock that formed when the rock contracted, most often during cooling. Columnar jointing is always a joy to observe in rocks in the field. Stumbling upon perfectly geometric columns of rock can only be described as magical. Even the …

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November 11, 2012

A Second Geologist’s Alphabet

I’m already at the letter B of my third geologist’s alphabet, so I thought I should compile a list of my second geologist’s alphabet. During the last year of my PhD, my weekly words were not so weekly. Thus, I blogged my second geologist’s alphabet over the last year and a half or so. My first geologist’s alphabet can be found here. Here’s my second geologist’s alphabet: A is for …

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Geology Word of the Week: B is for Botryoidal

A bunch of grapes which I purchased earlier today at the Woolworth's grocery store across the street.

def. Botryoidal: Shaped like a bunch of grapes. The word botryoidal comes from the Greek word “botrus”, which literally means a cluster or bunch of grapes. In geology the word botryoidal is often used to describe a rock texture or mineral habit (appearance). Here are a few pictures of some botyroidal rocks and minerals: ***Thanks to Patrick Donohue for suggesting this week’s word and to Patrick and Lockwood DeWitt for …

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November 4, 2012

Geology Word of the Week: A is for Amygdale

Amygdaloidal basalt collected during dredging along the Ninetyeast Ridge in the Indian Ocean in summer 2007.

def. Amygdale (also spelled Amygule): Vesicles, generally in extrusive igneous rocks, that are filled with secondary minerals, most commonly quartz, calcite, chlorite, and zeolite. When a rock contains amygdales, geologists often describe it as an amygdaloidal rock. For example, basalt is often described as amygdaloidal basalt. Here are a few previous, related geology words of the week that may be of interest: V is for Vesicle (and Vug) Z is …

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October 28, 2012

Geology Word of the Week: Z is for Zeolite

Natrolite, a mineral belonging to the zeolite group. Mary's Peak, Oregon. Picture courtesy of Dana Hunter.

def. zeolite: The name of a large group of porous, framework, aluminosilicate (their basic structure is interlocking tetrahedra of SiO4 and AlO4) minerals that contain significant water and also significant exchangeable cations, which makes them absorbent materials. The name zeolite originates from the Greek words “zeo”, which means “to boil”, and “lithos”, which means “stone”. Zeolites were given their name because when you heat them, they generally release water in …

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October 19, 2012

Geology Word of the Week: Y is for Yellowstone National Park

Yellowstone #2. Fall 2005.

def. Yellowstone National Park: A United States national park that is located in the states of Wyoming, Montana, and Idaho. Established in 1872, Yellowstone was the first national park to be founded and set an example for other national parks which were subsequently established all over the world. The park is the current location of the Yellowstone hotspot, which is responsible for large-scale volcanism in Oregon, Nevada, Idaho, and Wyoming. …

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