Transcript Andrew`s HS BB Creek

Geology of High Point, N.C.
Linda Kennedy, Department of Geography, UNCG, July 2011
Geology of High Point, N.C.
High Point is located on rock that formed during the Paleozoic Era (between 570
and 286 million years ago). Rock exposures are not typically common on the
Piedmont because the bedrock is covered by a very thick mantle of soil.
However, Boulding Branch creek has eroded and removed enough soil in places
to expose the underlying bedrock.
Geology of High Point, N.C.
Bedrock is exposed in Boulding
Branch Creek, in at least three
locations:
1. Bedrock Bridge
Andrew’s HS
Two-mile marker
2. Two-Mile marker
3. Safe Haven
Geology of High Point, N.C.
Location: Two Mile Marker
Bedrock exposed
in middle of
creek
Geology of High Point, N.C.
What type of rock is exposed in
Boulding Branch Creek?
How was the rock formed?
What has happened to the rock
since it was first formed?
Rock Type
Andrew’s HS
BB Creek
Rock exposed in Boulding
Branch creek is intrusive
volcanic rock that has been
later subjected to stress,
resulting in metamorphism.
P.A. Carpenter, III. 1982. Geologic Map of Region G, North Carolina. North Carolina Department of Natural Resources
Rock Type
Intrusive volcanic (igneous) rock
Rock Type
Intrusive volcanic (igneous) rock
Granite
• cools very slowly
deep in the crust
• relatively large mineral
crystals have time to form
– described as coarse
grained
• granite and diorite
are examples of coarse
grained intrusive volcanic
(igneous) rock
Diorite
Rock Type
Metamorphism
At a later date, the volcanic rock was exposed to
extreme pressure/stress and temperatures,
resulting in the recrystalization of minerals.
Life History of Boulding
Branch Rock
Formation of Pangea
North Carolina
The rocks exposed in Boulding
Branch creek were originally
formed PRIOR to the formation
of the supercontinent Pangea,
but are an important
part of the Pangea story.
The Piedmont of North Carolina
was at the center of Pangea action!
Before Pangea
Volcanic
Chain
N.C.
485 Ma
http://www.jan.ucc.nau.edu/~reb7/nam.html
Iapetus
Ocean
The Iapetus Ocean
once separated
North America from
Africa. It was the
closing of the Iapetus
Ocean that resulted in
the formation of
Pangea.
North Carolina looked very
different at that time. Neither
the Piedmont nor the Coastal
Plain existed.
As the ocean closed,
a chain of volcanic
islands gradually
moved toward North
America.
Before Pangea
http://www.jan.ucc.nau.edu/~reb7/nam.html
http://www.jan.ucc.nau.edu/~reb7/nam.html
Microcontinent
N.C.
430 Ma
400 Ma
When they collided, a portion of the volcanic islands were accreted
(scraped) onto the eastern edge of the North American continent.
As the Iapetus continued to close, a small portion of continental
crust (a microcontinent) moved towards North America.
Before Pangea
http://www.jan.ucc.nau.edu/~reb7/nam.html
http://www.jan.ucc.nau.edu/~reb7/nam.html
N.C.
345 Ma
315 Ma
Some of the microcontinent was also accreted onto the eastern edge of
North America. Ongoing closure finally resulted in Africa colliding with the
North American continent.
290 Ma
Pangea
formed
N.C.
Formation of Pangea
Volcanic island chain
moves westward.
Volcanic chain collides
and is accreted onto
eastern edge of N.A.
microcontinent moves
westward.
Microcontinent collides
and is accreted onto
eastern edge of N.A.
African continent
collides with N.A.
forming Pangea.
Rock of the Outer Piedmont
Formation of Outer Piedmont
The rocks underlying High Point began life as
magma that cooled deep in Earth’s crust
below a chain of volcanic islands
The volcanic chain formed over a subduction
zone located close to the eastern edge of the
North American continent
The subduction occurring off the eastern
coast accreted (scraped) some of the volcanic
rocks onto the edge of the North American
continent. The later collision of North America
and Africa resulted in the formation of Pangea
and the metamorphism of the accreted volcanic
rock
Presently
Presently, Piedmont rock is being weathered,
eroded, and ultimately transported to the
Atlantic Ocean where it is deposited as sediment.
This sediment once compacted and cemented will
become the sedimentary rock of the future.
Examination of sediment in Boulding Branch Creek
indicates that human manufactured particles of
glass and plastic are abundant, and it is therefore
possible that future sedimentary rock will contain
human made debris!
Resources
General
Lesson plans/Activities
N.C. Department of Environment and Natural Resources
http://portal.ncdenr.org
Geosphere links for teachers
http://nesen.unl.edu/scienceresources/linksgepsphere.asp
United States Geological Survey (USGS)
http://www.usgs.gov
Resources for K-12 Earth Science Educators
http://www.geosociety.org/educate/resources.htm
N.C. Geological Survey
http://www.geology.enr.state.nc.us
USGS resources for secondary schools
http://education.usgs.gov/common/secondary.htm
USGS Studies in N.C.
http://pubs.usgs.gov/fs/fs-033-96
Mining Institute
http://www.mii.org
Relief Map of North Carolina
http://geology.com/shaded-relief/southeast.shtml