Folds.jpg (14453 bytes)

.TOURING

COLORADO GEOLOGY

Trilobite.jpg (14302 bytes)

GLOSSARY

batholith a large discordant pluton with an outcropping area greater than 100 square kilometers
boulder particles greater than 256 mm in size
000613bd East Side of Monarch Pass.JPG (174509 bytes) cirque a large bowl-shaped hollow carved out of a mountain by a glacier
clast a rock/mineral fragment
000710bd Roadcut at 285 and 470.JPG (243672 bytes) clastic sedimentary rock a sedimentary rock composed of fragents of rocks/minerals (clasts)
clay particles less than 1/256 mm in size
coarse-grained grain sizes greater than 2 mm
cobble particles ranging in size from 64 to 256 mm
concordant parallel to bedding planes, rock layers, or foliation
discordant not parallel to bedding planes, rock layers, or foliation

000711bg Dome near Pine.JPG (232805 bytes)

dome a smoothly rounded rock exposed mountain usually formed by the process of exfoliation
dyke a discordant, planar, intrusive igneous body (contrast with sill)
era major subdivision of the geologic time scale (e.g., Paleozoic, Mesozoic, Cenozoic)
000718cs.JPG (247622 bytes) erratic boulder transported by a glacier and deposited some distance from its source
000720bd.JPG (353297 bytes) exfoliation the peeling away of rock layers from the outer surface of a large rock
extrusive rock an igneous rock formed at or near the earth's surface
evaporite
000714bt.JPG (376634 bytes) fault a break in the rock layers where movement has occurred.
felsic silica-rich igneous rock (light colored)
ferromagnesian minerals containing iron and magnesium (usually dark-colored) such as biotite, hornblende, augite, and olivine.
foliated/foliation
glacier a large, permanent mass of ice, formed on land and which moves due to its own weight

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igneous a rock formed from the cooling down and solidification of magma.
intrusive an igneous rock formed below the earth's surface
Untitled-8.JPG (306162 bytes) joint/jointing a fracture or crack in rock with no displacement
mafic ferromagnesian rich igneous rock (dark colored)
Untitled-6.JPG (412780 bytes) metamorphic a rock which has been altered due to pressure and/or temperature.
migmatized a mixture of igneous and metamorphic rocks
Calcite3.JPG (41454 bytes) mineral a naturally occurring, inorganic, crystalline solid that has a definite chemical composition.
000714ba Till near Santa Maria.JPG (430669 bytes) moraine a body of till deposited by a glacier
mylonitized
non-foliated
organic sedimentary rock rock composed primarily of plant or animal remains
pebble particles ranging in size from 2 to 64 mm
pegmatite extremely coarse-grained igneous rock
pluton body of igneous rock formed below the earth's surface
porphyry/porphyritic an igneous rock with large crystals enclosed in a fine matrix
Pre-Cambrian the period of time prior to the Paleozoic Era.  Rocks older than about 590 million years.
ptygmatic fold
rock a naturally formed material composed of one or more minerals.
sand particles ranging in size from 1/16 to 2 mm
000710bd Roadcut at 285 and 470.JPG (243672 bytes) sedimentary rock formed from the lithification of any type of sediment, precipitation from solution, or consolidation of the remains of plants or animals.
shear/sheared/shearing
silt particles ranging in size from 1/256 to 1/16 mm
000714ba Till near Santa Maria.JPG (430669 bytes) till unsorted chaotic deposit of rocks deposited by a glacier
weathering processes that change rock at or near the earth's surface.
000718bb.JPG (311032 bytes) xenolith foreign rock fragment "floating" in an igneous rock

Updated 04/24/03.

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