The Earthquakes of China

2008 Wenchuan Earthquake

Recently, in the last few years, many earthquakes have occurred in China.  Just a few days ago, there were approximately 200 deaths due to an earthquake which happened in the same area as a devastating event about 5 years ago.  The Wenchuan Quake of May 2008 found tens of thousands dead or missing. 

 

The epicenter of the recent event is near the eastern foothills of the Himalayas.  This mountain range is still forming because the Austro-Indian plate is pushing into the Eurasian plate.  Rock underneath the surface has been crushed and rolled right on top of one another, causing an uplift. 

 

The Earthquake that took place April 20, 2013

This phenomenon is similar to when one has a sheet of paper and pushes one side against another.  The paper "rolls."  If one squeezes the paper on a flat table surface, the paper rolls upward.  This experiment shows how it is that mountains are formed.

 

Being near a mountain range during an earthquake could be quite dangerous due to landslides and mass wasting.  Massive boulders on top of the mountains can easily tumble over, destroying anything in it's path.  Add to this faulty building codes, subsidence that compromise foundations along with countless of people trapped in a confined area and one has a recipe for an astronomical environmental  hazard.  This is what happened five years ago and it is what happened less than two weeks ago. 

 

Another cause of the landslides and mass wasting is due to the fact that the Himalayas are getting very high.  These humongous mountains will eventually collapse on itself, simply because of the weight.  This is the mountain range that is home to Earth's highest peak, Mt Everest, which rises 8,848 meters above sea level (29,029 feet).   Amazing thing, this plate tectonics!

 

 

 

 

Though most of us see earthquakes as a "bad" thing (myself included), this phenomenon is actually a good thing.  It is a side effect of a process that keeps life on Earth possible.  Without plate tectonics, volcanoes wouldn't be.  Though volcano can be quite destructive in of itself, fresh basalt deposits renews the surface, adding much minerals that allows vegetation to be sustained.  Plate tectonics also is a sign that our home is indeed alive and is constantly renewing herself.  Our oceans are constantly, though slowly but surely, changing, giving Earth a chance to go through these cycles of constant birth and rebirth.  I do admit, however, that it is unfortunate that these events do happen when they do, wherever they do occur.  

 

It is a constant reminder just how precious human life really is. 

 

From Fayetteville, AR USA

--GeoJack

 

 

 

 

Clear Waters From Clear Fork River

Notice the V-Shaped Valley in the upper left corner
There is a creek that runs through there and will empty into
the Clear Fork of the Cumberland River just
downstream from here.

Many people have a river or creek that runs through their village, town or city.  Especially if they live in Karstic regions in moderate zones.  Take, for example, the Ozark Plateau or the Ouachita Mountains in Arkansas along with, Southeast Kentucky and Northeast Tennessee, down the western slopes of the Southern Appalachian Mountains! 

But what if there are some rapids like the image to the left, the "Train Wreck Rapids," as it is affectionately known by whitewater enthusiasts, that is on the river or stream that is floating by? The Clear Fork of the Cumberland River is no exception to the rules that many other Karstic rivers have.

Map of the Clear Fork Basin

The Ouachita Mountains of Arkansas has ridges that run east to west.  This is why rivers generally flow eastward there.  The Appalachian Mountains has a series of ridges that run southwest to northeast. It would make sense that rivers in this area will flow downhill following these paths.  Of course, rivers will form valleys by cutting their beds, moving sediments downstream, changing courses over time, creating their own little flood valley.  

Erosion is taking place here.
Notice how the rainwater over many years have
cut through the ground, creating it's own
stream-bed.  This may become a stream one of
these days!

Clear Fork starts in Bell County, Kentucky, where Tennessee and Virginia border in the southeast corner.  This would make it real close to the Cumberland Gap.  The river runs southwest to west southwest, (which tells us that the elevation is getting lower in this direction) entering the state of Tennessee, where it continues to flow in a southwesterly direction and then curves to the west and northwest.  When the river starts to flow northerly, there must be a ridge just to the south of where the river bends.  There is an opening to the west that is lower than the south, therefore, Clear Fork will take a westerly then a northerly direction, as it continues to go downhill.  Clear Fork reenters the State of Kentucky in the county just to the west of it's origin, Whitley County.  Here, the river flows into the Cumberland, just east of Williamsburg, the county seat.

A road runs right by the Clear Fork (to the right of the road).
The cliff face to the left was made by human activity
when creating a path for this road.

The Clear Fork River, right before flowing into the
Cumberland River just east of Williamsburg, KY

In Claibourne County, Tennessee, there is a city that sits where Interstate 75 goes north into Kentucky (also where the river is).  This town is Jellico and it is the home of the Clear Fork Watershed Council.  I know, because I have a cousin, Derek Douglas, who is heavily involved with that Community Organization.  It is he, that I must thank for posting these fascinating photos, which he so kindly allows me to publish here!  For more information, please visit their facebook page, 

https://www.facebook.com/pages/Clear-Fork-Watershed-Council/141815149225594

That's a nice looking cliff face! I can tell that it has gone through it's share of erosion. That "tannish" color was recent, where the rock fell out. Eventually, it will turn into the bluish-gray, blending with the surroundings. I notice to that the top extends further out above the road than the bottom does. When its freezing, the water that runs through these rocks will turn to ice.  When this happens on a continual basis (freezing, thawing, freezing, thawing, etc.), the rock formation will eventually break because of the stress, causing this discoloration to occur.  From this photo, I can tell there is a lot of limestone in the area, so this is definitely Karstic, with it's share of spring-fed creeks and streams, along with numerous caves.

Thanks!
Jack Douglas

Geologic Hazards: Sinkholes

In wake of a recent tragedy near Tampa, FL last week, the country reels back and realizes that sinkholes can become deadly.  There are three known deaths in Florida due to sinkholes throughout the state's history, so fatality isn't really associated with this phenomenon.  However, loss of life can and does occur.  What is more, sinkholes are associated with karstic topography, thereby making up 10-15% of the total Earth's surface that are prone to these hazards, as the purple areas on the Circle of Blue map shows. 

Map taken from "Circle of Blue"

The United States Geological Survey (USGS) define sinkholes as, "an area of ground that has no natural external surface drainage--when it rains, all of the water stays inside the sinkhole and typically drains into the subsurface. Sinkholes can vary from a few feet to hundreds of acres and from less than 1 to more than 100 feet deep. Some are shaped like shallow bowls or saucers whereas others have vertical walls; some hold water and form natural ponds. Typically, sinkholes form so slowly that little change is noticeable, but they can form suddenly when a collapse occurs. Such a collapse can have a dramatic effect if it occurs in an urban setting."

Map taken from: Northeastern University

On the map from Northeastern University, the green colors (both light and dark shades) represents areas with carbonate rocks underlying the ground.  This is typical of karstic topography, because karstic rock is sediments such as limestone and dolomite embedded into the bedrock.  These dissolve with rain water because the acid in the precipitation reacts with the carbons in those rocks.  This explains the large amount of caves inside karstic areas.  Note Eastern United States and the look at Florida.  The Ozarks of the Central US has also this danger.

Image taken from CBS News

Tropical storms and hurricanes can dump a lot of precipitation on a localized area.  If underneath that area lies a limestone cavern, the top of that cave could collapse, causing these sinkholes.  In June of 2010, one such storm did just that in Guatemala, causing a deep sinkhole.  A photograph from CBS News looks "photo-shopped," but is indeed an accurate picture of what happened there.  A massive hole like that could definitely swallow automobiles and buildings, with damages excessive in terms of money and human lives.  

Urban sprawl is also a culprit in the making of sinkholes.  When urbanized regions become really built up, the land has to support more weight.  The bigger the cavern underground, the less support the ground has.  The ground sinks because it cannot support the weight above the surface.  Because of these urban sprawl and tropical storms along with having a karstic underground, Florida more sinkholes than any other state.

Image taken from USGS

A big concern of sinkholes is flooding.  Often times a new pond that just appears is a sign that a sinkhole is on its way of being formed, because a depression in the land occurs before the collapse.  If someone is building a house on level ground that person may not know that he or she is building upon a future sinkhole.  Some time later, a depression forms and rainwater will naturally collect there, having no other place to drain off to.  This causes more weight upon the unstable surface and a positive feedback is made, where one thing leads to another and then the inevitable occurs.  The ground literally caves in, slowly at first, but more and more things happen that will quicken the process.

Image taken from "About Geology"

Flooding also occurs because of what is happening underneath the surface.  Rainwater dissolves the carbonates, forming caverns underneath the ground.  As a result, there is no place for the water to escape to and gets trapped down there.  Through the process of erosion, water essentially gets blocked in with no drainage to get out.  When a sinkhole forms, a pond may appear as water comes back above the surface due to the sunken ground, called subsidence, forces the water up.

Because depressions are a usual sign of a sinkhole, people naturally uses these geological features as a pit to throw garbage in.  This is also an environmental hazard because it could very easily contaminate the local drinking water supply.  This is why many communities have laws regarding what and where one could dump wastes. This is also a reason why many landfills today in America are heavily regulated.  Illegal dumps can also cause blockage of water, so it cannot drain out.  The unsupported ground has that much more weight and collapses.  Again, positive feedback is in play here.  

The scientists at "How Stuff Works" have this to say in how to detect if a sinkhole may be forming around the house that one is buying.  "Property damage, especially around the foundation, may be a subtle sign that something is wrong. In addition, if vegetation is dying unexpectedly, a sinkhole may have disrupted underlying streams that usually feed the plants. Other signs to look for include polluted or muddied well water, formation of new ponds and trees, or sign posts that appear to be slumping over."

Image taken from "How Stuff Works"

Of course, no one should buy property to live on if the neighborhood looks like swiss cheese!  Often times though, potential geologic hazards do not present themselves as obvious as the above image.  If it did, life for many would be much smoother.  Yes, that is safer, but ultimately, where is the fun in that?  Oh, yeah.  investments and capital interests.  Got it.  Maybe information such as this is important after all!

Introducing America's First National River

High up in the Boston Mountains of Northern Arkansas, somewhere in Southwestern Newton County rises the first National River in America, the beautiful and WILD Buffalo!  It runs approximately 240 km (slightly more than 150 miles) and empties into the White River at the Marion/Baxter county line just south of Flippin, Cotter and Gassville, Arkansas.

http://www.nps.gov/buff/planyourvisit/index.htm

 

Figure 1 National Park Service Website

 

The river is particularly known for its amazing vistas and canoeing/kayaking activities.  The National Park Service has made the lower 217 km (approx. 135 miles) into a park.  The remaining upward part of the river is part of the Ozark-St. Francis National Forest.  It is the park where the River becomes a National River (see Figure 1).   The US Army Corp of Engineers was planning to dam this river up, but in 1972, Congress said no, and made the river into a park, out of concern for the flora and fauna habitats and thereby preventing any commercial/industrial uses out of the land that might disrupt the nature of the area.

The river actually starts 24 km (15 miles) inside the park area where the Main Prong of the Big Buffalo Creek joins Reeves Fork north of Fallsville, AR.  From there, it goes roughly due east until it joins the White River.

Advanced kayakers and canoeists love the challenging section called “Hailstone River.”  It is 15 miles up the river (south) of Boxley, AR (where State Highway 21 crosses the river) and runs right down to that bridge.  This section of the river should only be used by canoeists when the water is really high and by those with solid whitewater skills.

Figure 2 Photo taken by David Orr

The upper part of the river is steep and riddled with limestone and sandstone cliffs.  There are numerous falls located throughout this part of the Buffalo.

Amongst other activities popular here is fishing and camping.  

The Park Headquarters is located in Harrison, AR