Theodore Roosevelt National Park Part II: North Unit
The entrance to the South Unit of Theodore Roosevelt National Park is located right in the town of Medora, ND, while the North Unit is located about an hour's drive to the north of Medora and the interstate. Consequently, the North Unit doesn't get nearly as many visitors as the South Unit. That's too bad, because many people (including us) think the North Unit is more rugged and the contrast between the grasslands and badlands is strikingly more beautiful than the South Unit.
During the Ice Age, glaciers reached down out of Canada as far as the northern boundary of the North Unit. Ice sheets dammed the rivers that previously flowed north to Hudson Bay causing them to flow east and south to the Mississippi. The new courses of the rivers were steeper causing the rivers to flow faster. The faster flow in the area that is now the North Unit caused the rivers erode away more of the soft, sedimentary rock creating deeper canyons and gullies than in the South Unit.
This year, especially since we have been traveling across the northern part of the country, we have been encountering landscapes that have been influenced by melting glaciers. We keep wondering what caused the glaciers to melt so long ago before the existence of man-made greenhouse gases that are being blamed for global warming today.
Not only are the canyons deeper, we think there is more contrast and more color in the layers of sediment in the North Unit. The photo below shows typical layering and colors in the North Unit.
The road in the North Unit extends into the park for a distance of 14 miles. The road is currently undergoing extensive renovation, and some stretches (especially at the eastern end of the park) are gravel. We hit a couple of brief construction delays, but nothing major.
Slump blocks are common feature in the North Unit. Because of the deeper valleys in the north, large blocks of the soft rock and clay sometimes break free and slide down into the valley more or less intact. You can easily spot the slump blocks because the layers are sloped rather than being horizontal. The next photo shows one of several slump blocks located a short distance into the park.
The next formation shows how the layers erode differently. Harder layers about one third and about two thirds of the way down have created steps with strong vertical lines in the softer layers below.
The thick, softer layers of the formation in the above photo are also host to hard inclusions called concretions. Concretions are deposits of cement-like mineral, frequently a calcite or silica, that form around a seed grain and grow within the porosity of the softer sediment layer. The concretions can be as small as a grain of sand or up to 10 feet in diameter such as some of those at Theodore Roosevelt National Park. The one in the foreground in the photo below is about 6 feet in diameter. You can see other concretions embedded in the hillside. Although they can be other shapes, the concretions are usually round or ovoid.
A little farther along the road, we stopped at Caprock Coulee Trail. Coulee is another name for a deep, dry stream bed or gully. Caprock Coulee Trail is almost two miles long; but since Margery was fighting a cold and feeling a little under the weather, Paul hiked the first three-quarters of a mile of the trail by himself. The first part of the trail is a nature trail, and maps are available with descriptions of formations and plants along the way. The trail follows a coulee and provides closeup views of the colorful strata. Notice the caprocks sticking out of the left side of the hill near the top.
There were more caprocks near the bottom, too.
A little farther along, there was also a good view of a slump block to the right at the bottom of the cliff.
There was quite a bit of petrified wood along the wall on the far side of the coulee and at the end of the nature trail. The petrified wood here is much less colorful than that at Petrified Forest National Park in Arizona that we visited earlier this year.
As we continued driving the park road, we came to a pull-off overlooking an "S-bend" in the Little Missouri River. The shelter overlooking the river was built in the 1930s by the CCC (Civilian Conservation Corps).
There was more red scoria at the overlook.
From the river overlook, the road turns north toward the northern boundary of the park. On the north side of the road, there were rolling grasslands as far as you could see. We saw several herds of bison grazing.
On the opposite side of the road, there were badlands stretching to the river valley.
This area near the northern boundary of the park marks the southern edge of a glacier that existed here during the Ice Age. This is evidenced by the presence of stray boulders, called "erratics." They are called erratics because they don't match any of the local rock and they really don't belong there. They were carried from several hundred miles away by the glacier.
At the end of the park road is Oxbow Overlook. An oxbow is a lake that is created when a river changes course and a curve of the river is cut off leaving a lake. The oxbow along the Little Missouri is dry only fills with water during floods. The photo below shows the bend in the river near where the oxbow is located. We weren't sure of the exact location of the oxbow since it was dry when we were there, but we think it is on the gray-colored plain to the left.
From Oxbow Overlook, we retraced our route back to the visitor center, then back to the motor home. Fortunately, we were able to pass through the construction areas in the park with no delays on our way back.
From Medora, we headed east and then south. As our summer sightseeing winds down, we'll still have some interesting stops along the way, so keep looking for our posts.