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From: Dan Richter (1:317/3)
To: All
Date: Mon, 17.05.21 13:00
ES Picture of the Day 17 2021
EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes
and phenomena which shape our planet and our lives. EPOD will collect and
archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Madison Limestone in the Little Rockies of Montana

May 17, 2021

EPODbenson

Photographer: Rod Benson

Summary Author: Rod Benson
These light-colored cliffs are made of nearly vertical layers of
Madison limestone, formed from sediment deposited during the
Mississippian Period about 340 million years ago. Thick deposits of
corals, shells, and other forms of calcium carbonate
accumulated on the floor of a shallow tropical sea when this part of
Earth’s crust was much closer to the equator. The hiker in the blue
shirt provides a sense of scale.
The sediment was deposited in horizontal layers, but about 60 million
years ago magma worked its way up toward the surface, causing the
Madison Limestone to be domed upward. Eventually, the magma
hardened, becoming igneous rock ( syenite porphyry), which forms the
core of the mountain range. The doming occurred in an area about 15-20
miles (24-32 km in diameter. Over time, most of the limestone above the
igneous intrusion eroded away, leaving only the steeply- tilted edge of
the limestone dome that forms the cliffs shown in the photo. Many
other similar outcrops can be found around the perimeter of the
Little Rockies. Photo taken on March 19, 2021.

Hays, Montana Coordinates: 47.9892, -108.6943


Related EPODs

Madison Limestone in the Little Rockies of Montana Granite in
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Guatemalan Volcanoes Kasha-Katuwe Tent Rocks National Monument,
New Mexico Caldera de Taburiente National Park, Spain
More...

Geology Links

* Earthquakes
* Geologic Time
* Geomagnetism
* General Dictionary of Geology
* Mineral and Locality Database
* Mohs Scale of Mineral Hardness
* This Dynamic Earth
* USGS
* USGS Ask a Geologist
* USGS/NPS Geologic Glossary
* USGS Volcano Hazards Program

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Earth Science Picture of the Day is a service of the Universities
Space Research Association.

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