Like Superheroes, Rocks Have Layers
Brown County State Park: Land of Scenic Hills, Ridges, and
Valleys
The scenic "Hills of Brown County" were carved from sedimentary
rocks that formed about 300 million years ago when southern Indiana
was covered by a shallow inland sea. Sand, silt, and mud from
highlands to the northeast were carried into this sea by ancient
river systems and were deposited in a vast delta complex similar to
that of today's Mississippi River. These deposits later
hardened into __________, __________, and __________ that form the
Borden Group of rocks. Later still, the sea cleared, and
thick bed of __________ were deposited over these rocks.
Following regional uplift, the rocks were exposed to weathering
and erosion. After that time, hundreds of feet of these ancient
rocks were stripped away by the streams of those times, and the
scenic hills and valleys of this area were eventually formed. Where
more resistant __________ protected the underlying rocks, much more
prominent hills like Weed Patch Hill, Hohen Point, and others were
formed.
Taken from
Our Hoosier
State Beneath Us
prepared by Jian Liu and Anne
Graham, Reference
Department, IU Libraries in
collaboration with Lois Heiser Geology
Library, IU Libraries
and Indiana Geological
Survey,
IU
November 1998
These kinds
of rocks help make up the Geomorphology
of Brown County State Park. The coordinates will take you to
an area overlooking Strahl Lake. You can park at the Strahl
Lake parking area or at the Nature Center parking area.
Shale
Shale
rock is a type of sedimentary rock formed from clay that is
compacted together by pressure. They are used to make bricks and
other material that is fired in a kiln.
Limestone
Limestone
rocks are sedimentary rocks that are made from the mineral calcite
which came from the beds of evaporated seas and lakes and from sea
animal shells. This rock is used in concrete and is an excellent
building
stone.
Conglomerate
Conglomerate rocks are sedimentary rocks. They are made
up of large sediments like sand and pebbles. The sediment is so
large that pressure alone cannot hold the rock together; it is also
cemented together with dissolved minerals.
Gypsum
Gypsum rocks are sedimentary rocks made up of sulfate mineral and
formed as the result of evaporating sea water in massive
prehistoric basins. It is very soft and is used to make Plaster of
Paris, casts, molds, and
wallboards.
Sandstone
Sandstone rocks
are sedimentary rocks made from small grains of the minerals quartz
and feldspar. They often form in layers as seen in this picture.
They are often used as building
stones.
To log this cache, you must do
the following:
The layers of rocks you see at the coordinates and in the pictures
are made up of different kinds of rocks. Study the
descriptions carefully and email me what kind of rock makes up the
thin layers, and also tell which type makes up the very thick layer
at the top. Please give an approximate estimate of the width
of the thin layers and the width of the thick layer. (For
example - A thin layer of
__________ is about _____ in. or cm wide, and the thick layer of
__________ is about _____ in. or cm wide.) Also,
please submit a picture of yourself in front of the rock layers.