Geology of the National Parks Through Pictures - Black Canyon of the Gunnison

My next post about the Geology of the National Parks Through Pictures is...

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Black Canyon of the Gunnison National Park

A random trip down to Colorado last year brought us to Black Canyon of the Gunnison. A park that perhaps is as magnificent a canyon as the Grand Canyon, although not nearly as wide. 

Unfortunately I seem to have not gotten a picture of the entrance sign (I know, I don't know how it slipped by me either). So we will just go on with the regular park pictures. I definitely recommend clicking on these to blow them up. We decided to camp at the park, however the park is very straightforward. One road in and through the park, that same road you turn around on and head out.

 View of the canyon along the Rim Rock Trail, between the campground and the visitor's center.

 A view down the canyon from up on the rim. The majority of the rocks that make up the canyon walls are Precambrian Gneiss. The reason that the canyon is so deep, it is believed, is because of a similar event that happened at the Grand Canyon. The land surface was pushed upwards quickly, causing more down cutting in a river that was already entrenched. However, since gneiss is much harder than the softer sedimentary rocks of the Grand Canyon, the canyon here was cut deeper with walls that ran more vertical. 

 A view of the canyon from the Visitor's Center area.

 Another view of the canyon. You can catch a slight glimpse of the river in the middle of the picture, emphasizing the depth of the canyon.

 Across the canyon. 

 This is the "Painted Wall". The pink veins are igneous intrusions that formed pink pegmatite within the overall gneiss. 

 Down the canyon walls. 

 More canyon views. 

Straight down. The walls really are near vertical in most areas of the canyon. 

Down the canyon.

And since I have no entrance sign photo, here is a shot of one of our camping companions, not wanting to get out of her tent.

Geology in Pop Culture - License Plate Geology #2

I had done this once before but I will continue as long as I can find some suitable examples. Here is my next in my License Plate Geology series: "Tuff"

Tuff
noun, Geology.
1. a fragmental rock consisting of the smaller kinds of volcanic detritus, as ash or cinder, usually more or less stratified. (dictionary.com)

Random Geology Photo - Air Temperature Gradient on a Mountain Range

One of the things that I love most about the transition from fall to winter is the time of year when it is not cold enough for snow to fall in the valley but it will fall on the mountains as seen below. I had previously published a similar, although not quite as good (in my opinion), photo on this blog before.

The air temperature gradient as seen along the Oquirrh Mts in Utah.

As you move up in the atmosphere the temperature decreases. As described at onthesnow.com, this temperature gradient depends on the weather outside. On cloudy and snowy days the change in temperature is about 3.3°F per 1,000 ft in elevation or up to 5.4°F on sunny days. 

The best thing that I love about this picture is that it highlights the slope in the land. When you are driving out here you don't realize how much elevation gain there is driving south (the right side of the photo). As you can see the snow line meets the valley surface on the right (south) side of the image. The right (south) side is approximately 600-700 feet higher in elevation than the left (north) side of the image which runs into the Great Salt Lake (just off the picture to the left). The snow line then produces not only a topographic contour (line of equal elevation) but also a isotherm (a line of equal temperature). 

References
http://www.onthesnow.com/news/a/15157/does-elevation-affect-temperature-

GIS "Pro" Tips - Merging Rasters

Often in GIS you come across situations where you need to merge together rasters in order to have one file to work off of (Digital Elevation Models (DEMs), aerial images, etc.). I have found that it gets a bit tricky sometimes to merge those together and get everything to align properly and/or not have any issues. Below is a list of suggested guidelines to follow while merging together multiple rasters. This was started and expanded upon from advice by a co-worker while I was working my GIS job and I figured I would share it since I could never find anything on the internet that was as clear and concise.

Tool: In the search field type in “Mosaic to New Raster”

                 In the Mosaic to New Raster Tool:

Input rasters: Bring them in any order, doesn't matter.
Output location: Save them to a different folder from the one they're in.  It just seems to help thing from crashing. Assign it to the C Drive.
Raster Dataset name with extension: Short name (13 characters or less), no spaces.  Do not give it an extension.
Spatial reference: Blank. It'll revert to whatever the projection of the source rasters is, which is what you want.
Pixel Type: 32-bit float
Cellsize: Blank.  It'll default to the sources' cell size.
Number of Bands: 1
Mosaic operator: Last…unless they don't overlap and/or your data comes from multiple sources.
Mosaic Colormap Mode: Default.

The important part:
Click on the Environments button then click on Processing Extent. Pick one of your input rasters as your Snap Raster. This makes sure that your new cell edges match up with the original and that nothing shifts over.  This is real important with datasets that have large cell sizes, but you want your data to line up regardless.

This is one of those tools that doesn't work sometimes for no good reason.  If that happens, just try again.

When merging 2 overlapping rasters of different tile size

Sometimes you may want to combine rasters with two different tile sizes. This may be you have a DEM and you want to incorporate areas with higher resolution data like LiDAR within the DEM area. To do this within the Mosaic to New Raster tool:

1. Give the LIDAR DEM (or whatever the higher resolution data is) the mosaic operator highest priority.
2. Set cell size as the same as the LiDAR DEM (or whatever the higher resolution data is).
3. In environments:
1. Set the raster analysis to min of inputs cell size.
2. Use the LiDAR DEM as snap raster

Some useful information and websites

The USGS has a nationwide ~10 meter DEM map available for download for free.

The information is located at the National Elevation Dataset (NED): http://viewer.nationalmap.gov/basic/

You can find lots of free information available for various areas across the nation (DEMs, aerials, watersheds, etc.) and if you zoom into your area of interest you can find what information is available. The 10m DEM is referred to as the “1/3 arc-second DEM”. This means that it is approximately 1/3rd of a degree of latitude and longitude. The 1/3rd arc-second equals approximately a 10m DEM (A 10m DEM is a DEM where each pixel is 10 meters by 10 meters), while the 1/9th arc-second DEMs equal approximately a 3m DEM.

You can also find where freely available LiDAR data is located here:
http://earthexplorer.usgs.gov/

Geology Through Literature - Vanity Fair

The next up on my Geology Through Literature thread is Vanity Fair by William Thackeray. Vanity Fair was written in 1848 and follows a group of wealthy urbanites throughout the time period of Napoleon's reemergence from Elba and his eventual defeat at Waterloo. You can get my complete thoughts on the book/story over at my other blog - The Remnant, but for here I will just go into the geological or basic scientific aspects that are brought up in the story.

Chapter XXV

There was only one instance of geology brought up in the story but it was one I had not thought about before.

"Who'd think the moon was two hundred and thirty-six thousand eight hundred and forty-seven miles off?"

This made me question when we actually figured out the distance between the Earth and the Moon. This story was written in 1848 and that seems very early compared to our modern day scientific techniques.

According to Nasa, the Earth is an average of 238,855 miles away, not that far off of the 236,847 miles quoted in the novel. And actually the distance between the Earth and Moon changes depending on the orbit. It goes from 225,623 miles up to 252,088 miles away (Space.com). So in reality, the novels distance quote was spot on. 

The distance from the Earth to the Moon was determined way earlier than the 1800's. In 270 BC, Aristarchus derived the Moon's distances using a lunar eclipse. The Greeks had already known the Earth was a sphere and that the Moon orbited the Earth (since it was assumed everything orbited the Earth at that time). He used this information, along with the duration of one lunar orbit (~a month) and the time it takes to fully cross through the Earth's shadow during an eclipse to determine that the Moon is about 60 Earth's away from the Earth. Without the actual Earth radius though, this couldn't be more refined, until Eratosthenes determine the Earth's circumference a couple of decades later (as discussed earlier). 

More detail on the mathematics of Aristarchus' calculations can be found on Nasa's website: 

http://www-istp.gsfc.nasa.gov/stargaze/Shipprc2.htm

Another method was developed by Hipparchus to measure the distance between the Earth and the Moon using a total eclispe of the sun. You can read about his methods here:

http://www-istp.gsfc.nasa.gov/stargaze/Shipparc.htm

References

http://spaceplace.nasa.gov/moon-distance/en/

http://www.space.com/18145-how-far-is-the-moon.html

http://www-istp.gsfc.nasa.gov/stargaze/Shipprc2.htm

http://www-istp.gsfc.nasa.gov/stargaze/Shipparc.htm