Transcript Stearns County - geo

Stearns County was founded in
1855 and was named after
Charles Thomas Stearns, a
local politician.
The East border of Stearns
County is the Mississippi
River. The land consists of
rolling hills, scenic lakes, and
woodlands of a mixture of
coniferous and deciduous
trees. There are 166 lakes in
the county of Stearns.
From Wikipedia, the free encyclopedia
*Stratified sediment washed
out from a glacier by melt
water streams and
deposited in front of the end
moraine.
*Sand, gravelly sand,
and cobbly gravel.
imnh.isu.edu/digitalatlas/glossary/letter.asp
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Partially decomposed plant matter deposited in marshes.
› Includes fine-grained organic matter, marl, narrow deposits of
alluvium along streams, narrow beach deposits, and small bodies
of open water.
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In developed areas, many of these deposits have been
buried under artificial fill. The organic sediment is
commonly removed prior to filling in areas where major
structures are built.
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Mississippi River alluvium consists of generally less than
six feet of silt, loam-to-loamy sand, overlying sand,
gravelly sand, or cobbly gravel; also some scattered wood
and shell fragments.
Some depressions have been filled with thick silty to clay
like sediment.
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Bedrock at or near the land surface; consists of intrusive,
gneissic, and schistose rocks of Paleoproterozoic and Late
Achaean ages.
*The large block of banded Morton
Gneiss is about 3-3.5 billion years
old.
*The folded, metamorphosed,
banded iron formation is from the
Atlantic City mine in Wyoming.
*The Stromatolitic iron-formation
is made of fossil algae, from the
Mary Ellen Mine on the Mesabi
Range, a Biwabik Iron-formation.
It is 1.85 billion years old.
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Over a billion years ago, molten rock beneath
Stearns County surged toward the earth’s crust. As
the rock cooled, the minerals in the rock condensed
and hardened, forming deposits of very durable
granite.
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Outcroppings of these Pre-Cambrian rocks are
found in a 10 square mile area mainly between
cnesbau-export and Rockville. Colored granite
deposits were discovered here in 2007, which gave
the city it’s nickname of "The Granite City." These
porphyritic igneous rocks are a true granite of Early
Proterozoic age (1700-1800 million years ago).
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www.cnesbau-export.com/marble_export.html
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The main minerals evident in the rock are
quartz, potassium feldspar, plagioclase
feldspar, and biolite. Smaller amounts of
zircon, apatite, hornblende, chlorite sericite
and sphene also occur. The potassium
feldspars are the large crystals,
(phenocrysts), set in an otherwise equigranular matrix. The pink color of diamond
pink is due to pink coloration in those
particular rocks’ feldspars.
www.cnesbau-export.com/marble_export.html
Statue in front of
St. Cloud
Technical College
Plaza
Made of granite,
stainless steel and cedar.
St. Cloud
Quarry
Rainbow
Quarry
St. Cloud
Red
Granite
www.xekstone.com/NewsView.Asp?ID=19
www.merce.org/thecompany_ontherocks.html
*Slate forms when shale, which
consists of clay minerals, is put
under pressure with
temperatures of a few hundred
degrees or so. Then the clays
begin to revert to the mica
minerals from which they
formed.
*Slate is usually dark, but it can
be colorful too. High-quality slate
is an excellent paving stone as
well as the material of longlasting slate roof tiles. Slate also
makes the best billiard tables.
*Blackboards and handheld
writing tablets were once made of
slate, and the name of the rock
*With further metamorphism,
slate turns to phyllite, then schist has become the name of the
tablets themselves.
or gneiss.
www.xekstone.com/NewsView.Asp?ID=19
Sandstone is a sedimentary rock
composed mainly of sand-sized
minerals or rock grains. Most
sandstone is composed of quartz and/or
feldspar because these are the most
common minerals in the Earth's crust.
Like sand, sandstone may be any color,
but the most common colors are tan,
brown, yellow, red, gray and white.
www.xekstone.com/NewsView.Asp?ID=19
From Wikipedia, the free encyclopedia
Stearns
County, MN
www.saint-gobain.com/en/activities/constructionproducts/glossary
Gypsum is a mineral made up of calcium
sulphate hydrate. Gypsum is mined in
opencast quarries or underground galleries,
using specific drilling equipment and
nonpolluting explosives. Crushed and heated
in kilns, the gypsum is finally ground to
obtain plaster powder.
This unique
outcrop
shape is
the result
of erosion
of
weathered
bedrock.
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A gravel pit in south central Stearns County, Minnesota,
exposes sand and gravel of the Merden Lake esker which
is thought to have been deposited by a sub glacial stream
associated with the Wisconsinan-aged Superior Lobe of
the Laurentide ice sheet.
The presence of eskers indicates free melt water drainage
toward the glacier margin, and deposition occurs as flow
velocities are falling. The Merden Lake esker is a 1.5 km
long, sinuous ridge that begins in the very SW 1/4 of
Section 19, T124N, R29W and spans southwest through
the NW 1/4 of Section 30, T124N, R29W and ends in the
NE 1/4 of Section 25, T124N, R30W, Avon, Minnesota
(Stearns County, Minnesota) .
AMERICAN JOURNAL OF UNDERGRADUATE RESEARCH
Maps showing the location of the
Merden Lake esker in Stearns
County, Minnesota. The county
map (top right) shows general
glaciation. The topographic map
(bottom) shows relief of the esker
and the cross-sectioned region that
was used for excavation.
AMERICAN JOURNAL OF UNDERGRADUATE RESEARCH
Photograph of the esker as viewed from the
southwest. A-B corresponds to the label on
the topographic map in the previous slide.
The trench marker corresponds to a trench
depth of ~5 m. For scale, author Aaron
Hirsch is standing on a graveled slope
midway up the esker face.
Aaron Hirsch
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The Champion Dam played a role in the major
flood of 1965. Ice dams formed in a number of
unexpected places that year, causing large
pools of water to form. Once the ice dam
formed behind the Champion Dam, rising as
high as 24 feet above the normal water level,
the ice dam hit the ice breakers that are part of
the dam structure, and the ice dam let go. A
wall of water flowed down the Mississippi river,
overtopping the Saint Cloud dam. The surge of
water eventually flooded parts of Coon Rapids,
and contributed to the already serious flooding
in the Twin Cities area.
Champion Dam
Quarry Four in St. Cloud, also
known as “Oberg”, has one
of the best preserved faults
within the park.
This is a moderate sized
quarry with a maximum
depth of 57 feet located
in the north, where the
wall under water is
steep. Part of the wall is
exposed above water,
and part below; the
south wall is higher and
more steep than on the
north.
www.co.stearns.mn.us/.../Quarry4Oberg
Quarry ten displays good glacial polish. Most of the walls
of the quarry consist of glacial overburden.
Quarry Ten is
one of the
smallest and
more shallow
quarries in the
park. It has a
maximum
depth of 20 feet
and has a low,
swampy area
along the
eastside.
The southwest part
of this quarry is
continuous with an
outcrop that
exposes a contact
zone between red
and gray granite.
The outcrop has
many mini-faults
which may be
related to a larger
fault.
*Red granite is the dominant rock type in
Quarry Three. The most important geologic
feature is a wide dike of fine-grained, black
basalt located along the west high wall. This
is the only basalt dike oriented northwestsoutheast in the park and probably one of
only a few in central Minnesota.
*There are mini-faults at the north end, in
the middle of the east side, and in the
southeast corner. These faults probably
controlled the formation of the northwest
dike.
www.co.stearns.mn.us/.../Quarry4Oberg
*Excellent glacial polish
is found on outcrops at
the top of the south wall.
*Quarry Three is one of
the shallower quarries in
the park with a maximum
depth of 25 feet. Most of
the high walls are
bedrock.
www.co.stearns.mn.us/.../Quarry4Oberg
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On October 26, 1996, fourteen tornadoes touched
down in Central and West Central Minnesota.
Three tornadoes touched down in Stearns County
An F1 hit 6 miles South West of Belgrade to
Brooten, also touching down in Kandiyohi county.
Another F1 touched down 3 miles West of
Clearwater to 2 miles North West of Clearwater .
Minutes later, the third tornado, an F2, touched down
5 miles South, South West of Albany to 2 miles West
of Albany.
There were no fatalities throughout the entire state.
Tornadoes
forming
over Stearns
County
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Google
Hirsch, Aaron C., et. Al. “Analysis of the Merden Lake Esker, Stearns County,
Minnesota: A New Interpretation.” American Journal of Undergraduate Research.
3 Vols. College of St. Benedict/ St. John’s University: Collegeville MN, 2004. 3
Vols. 1-3.
Wikipedia
“imnh.isu.edu/digitalatlas/glossary/letter.asp”
“www.cnesbau-export.com/marble_export.html”
“www.xekstone.com/NewsView.Asp?ID=19”
“www.merce.org/thecompany_ontherocks.html”
“www.saint-gobain.com/en/activities/construction-products/glossary”
“www.co.stearns.mn.us/.../Quarry4Oberg”
“http://www.crh.noaa.gov/mpx/?n=26oct1996”