Geology in Gates of the MountainsGeology in Gates of the MountainsJuly 26, 2007. We are staying in Lincoln Road RV-Park Helena, Montana less than a mile west of I-15 at exit 200. Lincoln Road RV-Park is about 10-miles north of downtown Helena but in a very good position access everything in the area. $25.04 with Good Sam discount plus-taxes for FHU in nice gravel pull thru sites with some shade. Free wifi was available but no cable TV.
Cavities and caves visible in limestone cliffs
The side of this cliff is peppered with caves and holes all created by water. Limestone is porous and as such allows rain water to percolate through. However, water can and will dissolve limestone especially acid water. In any event water dissolves cavities. When these cavities are exposed in cliffs they become caves.
Titanic forces created these two different strata of limestone
Here is two different strata of limestone. That a appears to be a fault line where the earth literally parted and slid as one side was forced in one direction while the other in another direction.
Visible signs of tremendous uplift in the earths crust
This limestone has been contorted and bent until it is now in an almost vertical position. Keep in mind that this limestone was born on the bottom of an ancient sea some 350-million years ago. These limestone deposits are hundreds of feet deep and were in the making over possibly a 100-million years. Then this area was uplifted when molten lava deep in the earth exerted pressure. The sea floor became dry land then the seafloor continued to uplift. The limestone crust cracked and distorted as the pressure kept pushing it up. In the case of this rock it has been thrust up to an almost vertical position. At one time this mass of limestone was below sea level and now finds itself at over 4,000 feet above sea level.
Limestone cliff walls in Gates of the Mountains
The Missouri River has cut a path through this limestone creating these sharp banks.
Note the two different strata of limestone visible in this picture. There is a dark gray on the left side and a pale tan on the right. Titanic forces have uplifted and contorted these strata until you get what we see here.
Wedge of limestone imbedded in this exposure
The Missouri River has exposed this wonderful expanse of limestone. The wedge of rock has been engulfed by the surrounding rock. Not being a geologist I can not accurately determine what has taken place here but one layer of rock has engulfed another layer of rock creating a visible wedge.
Visual evidence of geologic forces in Gates of the Mountains Wilderness
This is another look at how geologic forces operate deep withing the earth. The tan material appears to be limestone since you can see the layers. the darker gray appears to me to be an intrusion of igneous rock that "intruded" into cracks in the limestone deep underground. It appears to me that what we are seeing is how deep underground the igneous rock almost surrounded that piece of limestone. Now the Missouri River has cut and exposed a cross section of that geologic event that happened millions of years ago during the uplift of this area.
Titanic forces have pushed this limestone into an almost vertical position
Smoke from the Meriwether Fire is making it difficult to see the geology but here the layers of limestone are nearly vertical instead of laying flat.
Look closely at the bend in that limestone formation on the left side of the picture. It is being formed into what geologist classify as an anticline. The arch shape in the limestone is an anticline.
Layers upon layers of limestone exposed in this bluff in Gates of the Mountains Wilderness
On the opposite side of the river limestone is laying horizontal just as it was formed over 300 million years ago. Yes, that is the Meriwether Fire burning in the understory. I cover the Meriwether Fire in the following travel logs:
2007 #129 Fire in Gates to the Mountains 2007 #129aa Meriwether Fire of 2007 2007 #129bb Helicopters Fighting Meriwether Fire 2007 129cc Fire Fighting Helicopters
Honeycone nature of limestone cliffs of Gates of the Mountains
This picture highlights not only the Meriwether fire but the honeycone nature of these limestone cliffs.
Yes that is smoke from the Meriwether fire. It looks like a small fire has started on that cliff.
Uplift forces have this piece of limestone at 45-degree angle
This limestone formation looks to be in about the 45-degree position. When the limestone was being created in a shallow ocean the layers were horizontal. Now that the ocean floor has been uplifted to an elevation of over 4,000 feet above sea level those forces pushing up have pushed and shoved the horizontal layers into this angle.
A geology question about this limestone exposure in Gates of the Mountains Wilderness
I wonder if those two bands of softer material might have been ash falling from a volcano. Or possibly this area was in a shallow bay with a river emptying into it. A flood or some other event may have carried a foot of silt into the bay causing these two bands.
Igneous rock meets limestone, in what appears to be a sincline
Look at the bottom left of this formation you can see where limestone the limestone formation ends around another rock is visible. The rock on the left is not limestone it is igneous in nature (molten rock). That igneous rock is what forced the limestone layer up. Sometimes it broke through cracks in the limestone. This is the result. I am not sure but this appears to me to be a sincline with the igneous rock in the middle of the sincline.
Osprey nest on top of a hoodoo in Gates to the Mountains Wilderness
This osprey nest high on that pinnacle caught our eye. It appears to be safe from predators on that perch.
The osprey nest is resting on the top of a hoodoo. Click here to learn what a hoodoo is.
Limestone hoodoos froming in Gates of the Mountains Wilderness
Note how erosion has carved these cliffs in the limestone. Those formations are called hoodoos.
Click here for more Montana Travel AdventuresUntil next time remember how good life is.
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Mike & Joyce Hendrix
Mike & Joyce Hendrix who we are We hope you liked this page. If you do you might be interested in some of our other Travel Adventures: Mike & Joyce Hendrix's home page Travel Adventures by Year ** Travel Adventures by State ** Plants ** Marine-Boats ** Geology ** Exciting Drives ** Cute Signs ** RV Subjects ** Miscellaneous Subjects
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