Macro-Geology - Tearing Down

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Landslides

Erosion

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Caves and Sinkholes

Glacial Features

· National Geographic video on landslides (sorry i-Phone & i-Pad, it’s in Adobe Flash!)

 

· To see another movie of an earthflow, click HERE.  Wait through the ad, it’s worth it.

Landslides occur worldwide and come in many forms (earthflows, rock falls, et al) and for varied causes.  These causes range from natural occurrences, such as earthquakes, to man-made, such as deforestation.  For more information, try Wikipedia by clicking HERE.

Text Box: Picture from the website of the USGS Landslide Program
Click to follow link

Erosion is the weathering-away of rocks into smaller sizes.  The main agents of erosion are water (running water, rain, ice) and wind.  Erosion is part of the rock cycle (click HERE for more info on the rock cycle) that recycles rocks of all types (igneous, metamorphic, and sedimentary) into building blocks for different rocks.  Without erosion, the Appalachian Mountains would be as tall as the Rockies. 

 

Erosion is visible in many forms.  River valleys and deltas, The Grand Canyon, Mammoth Cave, sandy beaches, waterfalls et al are all erosional landforms.

Macro-Geology can be explained in two broad categories:  Building, or Depositional, and Tearing Down.  Building includes activities such as volcanoes, earthquakes and of course plate tectonics discussed on the previous page.  Tearing down is another way to look at erosion.  The erosion agents of water and wind create some of our favorite places, for instance the Grand Canyon and Mammoth Cave.

Build It Up, Tear It DownText Box: To learn more about the Building processes, click in this box
Text Box: To learn more about the Tearing Down processes, read on below.

Canyons

Caves are openings in the Earth, usually large enough for a person to enter.  (Caves can also form in glaciers and other icy places, but won’t be discussed here.)    Caves are often formed by the action of water on rock.  Water can dissolve rock (common in limestone, gypsum, and calcite), erode rock,  or simply allow gravity to work (think sinkholes).  Volcanoes can also form caves, often tubular-shaped caves from lava cooling from the outside, insulating the still-molten lava at the interior.  Click HERE for some spectacular pictures of volcanic caves.  The wind and water together form sea caves.  The wind alone can form shallow caves.

 

Some famous (and not-so-famous) caves in the USA

· Mammoth Cave - Kentucky - the longest cave in the world - click HERE and HERE for more info

· Carlsbad Caverns - New Mexico -- click HERE for more info

· Lechuguilla Cave - New Mexico -- click HERE for more info

· Mark Twain Cave - Missouri -- click HERE for more info

Text Box: Bluespring Cavern
Bedford, IN
Oct. 17, 2011
Text Box: This cave features tours via boat.  Click on the picture for more info.
Text Box: Ohio Caverns
West Liberty, OH
Oct. 11, 2010

Michigan Sinkholes

Atlanta-to-Alpena, MI

 

Sinkholes are related to caves!  Sinkholes are formed by the collapse of caves, often the first indication that a cave lies underneath.  Sinkholes often form in areas where limestone lies underneath the surface. -- karst areas.

Carbon dioxide in the air is converted to carbonic acid by water.  This (exceedingly weak) acid seeps through the soil and rock.  When it gets to the limestone, the acid slowly dissolves the limestone, forming a cave.  When the cave gets so big that it cannot support its roof, it collapses into itself, forming a sinkhole.  Michigan has a line of sinkholes, running from Atlanta in the west to Alpena (and into Lake Huron) in the east.  Sinkholes sometimes connect to open caves, but connections in Michigan’s sinkholes have not been documented.

For more information about Michigan’s karst sinkholes, click HERE to link to an excellent overview of Michigan’s sinkholes (thx to Bill Houston for sharing) or click HERE to go to the Michigan Karst Conservancy’s website.

Text Box: This small cave lets visitors get close to the features.

Sinkhole on the Michigan Sinkholes Pathway near Atlanta, MI.  This sinkhole has a stairway to the bottom!

Stevens Twin Sinks, near Alpena, MI.  These two sinks are almost touching, as seen in the photo above.

Sinkhole at the end of Mystery Valley, near Alpena.  This sinkhole drains a seasonal lake.

Rivers that go underground, or re-appear from underground can be related to karst formations (Click HERE for more info from Wikipedia).  The Lost River in southern Indiana is a good example.  The river disappears in various locations depending on the seasonal weather, and re-appear, or ‘rise’ from sinkholes.  The picture on the right is the Wesley Chapel rise on the Lost River, while the picture at the left is the Orangeville rise, on a tributary of the Lost River.

Canyons are, well, pretty darn dramatic!  The deep crevices and steep walls inspire those that see them, and understandingly so.  Most canyons are carved by flowing water, but some are the direct result of tectonics - mountain-building.

 

Mention canyons and the Grand Canyon instantly comes to mind.  It certainly is the standard by which all canyons are measured, but it is not the only canyon.  There are many photography-ready canyons with a day’s drive of the mid-Michigan area.  See some pictures of those below.

Cedar Falls (it was a BIT dry) in Hocking Hills State Park, Logan, Ohio (Picture taken 13Oct10)

Little Clifty Falls in Clifty Fall State Park, Madison, IN (Picture taken 5May11)

The gorge on the Sturgeon River, downstream of Canyon Falls, south of  L’Anse, MI.  (Picture taken 14Sep12)

Turkey Run State Park, west of Indianapolis, IN.  (Picture from the website of the park, click HERE to go to this website.)

Glacial features are common all over Michigan, more so in the northern part of the lower peninsula.  The link below takes you to a presentation by MMRC members with pictures of many glacial features in Michigan.

 

Tim Middleton and Cheryl Roggenbuck  --  Geology of Northern Michigan

Pictures of caves visited by club members