#redwall limestone

[earthstory]

You’ve probably seen the Redwall Limestone before

The Redwall Limestone might very well be the single most distinctive unit in Grand Canyon. Passengers flying overhead in airplanes can often make out its massive, red-stained faces.

The Redwall is a limestone from the Mississippian period. At this time, a great, warm, tropical seaway covered the Western portion of North America. All sorts of life lived in these seaways, forming all sorts of shells and leaving enormous piles of fossils and carbonates that wound up as hundreds of meters of limestone.

The Redwall contains very little sediment that isn’t carbonate. Most of the rocks in the Canyon have a silicic component even if they are limestones; in the Redwall contains <1%. That implies that the seaway was so extensive the shoreline was just a huge distance away. There just wasn’t any sediment supplied to this area other than the life.

The unit is rich in fossils and sedimentary structures, including crinoids, brachiopods, corals, bryozoans, ooids, cherts, and various types of cross-bedding.

Perhaps the most noteworthy feature of the Redwall limestone is that the rock itself is not red. The color is supplied from above; reddish sediments wash down from the shales above, painting the exposed surfaces of the limestone a brilliant red.

The sharp face of the Redwall occurs as a consequence of the behavior of limestone. Limestone erodes easily with water flow but doesn’t break up easily without water. Thus, in a mostly arid area like the Grand Canyon, the Redwall makes sharp cliffs that even climbers will struggle with unless the rocks are otherwise broken. But, where water does flow, spectacular waterfalls and caves can be found in this unit.

-JBB

Image credits: https://www.flickr.com/photos/grand_canyon_nps/7706754222 https://www.flickr.com/photos/alanenglish/4599793309

Sources: http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/redwall.htm http://www.bobspixels.com/kaibab.org/geology/gc_layer.htm#rl http://www.utahgeology.com/fm_redwall.php

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[earthstory]

Snowy canyon In 2012, the Grand Canyon was hit by a nice snowfall on December 24, creating a lovely winter landscape. Interestingly, you can make out the actual temperature structure of the canyon just from this photo. Look at the snow levels – the lowest level where I see any snow is on top of the Redwall Limestone. In other words, during that snowstorm, there was enough of a temperature gradient that the canyon’s upper levels were below the freezing point of water while the lower platforms of the canyon were warm enough to only see rain. -JBB Image credit: NPS https://flic.kr/p/dDVsqS

[earthstory]

South Kaibab Trail

[vollmerdp]

Grand Canyon: Bright Angel Trail on Ground Control to Major Mom

New Post has been published on http://thevollmerfamily.com/MajorMom/2014/09/grand-canyon-bright-angel-trail.html

Grand Canyon: Bright Angel Trail

One of my favorite photos ever. My boys enjoying America’s beauty.

On the 2nd full day of our Grand Canyon trip, we decided to get an early start and hit the Bright Angel Trail.

The Bright Angel Trail originates at the heart of the “touristy” part of the South Rim Grand Canyon park. It’s a well-maintained trail, in part because this is the trail that the mules use for those tours. Because of the accessibility, it’s definitely more crowded than the remote Hermit’s Trail.

We drove our vehicle from the campground and found some parking about 1/2 mile from the trailhead.

At the Bright Angel Trailhead, which is adjacent to the Bright Angel Lodge.

The trail itself is very easy to negotiate. The kids had no problems, and I didn’t even have to worry about their getting too close to the edge; there was plenty of width to most of the trail.

In addition, we went early enough in the morning that much of the trail was still in shadow, although on our way back up to the rim, it became quite sunny.

If you get up close and personal below the rim, you find quite a bit of wildlife. I was surprised at how many trees and animals could be seen.

We hiked approximately 1 1/2 miles down the trail, perhaps 750′ down. We were attempting to go down five layers: that was the goal Jacob had set. He wanted to see the iron-rich Redwall Limestone layer. We barely got down to that layer before I decreed we needed to turn around. I got too nervous to go any further with the boys.

It’s important to remember that any venture down below the rim requires you to come back UP from any distance you choose to descend. This makes for a very daunting task. I was constantly worried that, the further we descended, the more difficult it would be for Timmy to come back up. He isn’t as enthusiastic about hiking as his brother.

However, Timmy did just fine. He enjoyed the Grand Canyon hikes quite a bit.

We spent just over two hours on the hike. We took several breaks on the way up, stopping for snacks and water. We talked to several other parties who were hiking at about the same speed we were. It’s remarkable learning how far away people travel to see the Grand Canyon.

After we got back up to the rim, we stopped for ice cream at the Bright Angel Lodge soda fountain.

If you ever go to the Grand Canyon, take a trip below the rim! You’ll be glad you did. The geology is amazing! The Bright Angel Trail is perfect for beginners.