Lost Mine Trail, Big Bend National Park, Texas

by Anonymous

Tremendous pressures within the globe’s interior caused the earth’s surface to rise in this region and the waters to recede. Much of the area became swampy, forming suitable habitat for the giant dinosaurs. Peat beds were compressed to form coal deposits. The remains of these coal beds as well as of petrified trees and dinosaur bones may be seen in the rock exposed in various parts of the park. At a still later date there were more extensive earth movements which caused great breaks to occur in the earth’s surface.

Sierra del Carmen in Mexico

Generally speaking, the geologic structure in the Big Bend area is a “sunken block” that might be compared to cutting through the elevated landscape twice. One cut is along the Sierra del Carmen mountains on the east, and the other at Santa Elena Canyon on the west. The area between the two cuts has sunk an average of several thousand feet. The central part of this block has been arched upward forming the Mariscal, Chisos, and Christmas Mountains.

Part of this uplift was caused by volcanic activity. Large masses of molten rock pushed toward the earth’s surface and arched and deformed the overlying sedimentary layers that had long before been deposited on the floor of the ocean. The Chisos Mountains were formed by this volcanic pressure.

As you look south or north, you see an extensive plain that is underlain very largely by sedimentary rock layers. The isolated peaks for the most part were caused by hot lava that pushed up from below, then cooled to make the present highlands. This is also true of the Chisos Mountains which are a much larger mass. Cooling of these melted rocks caused fracture joints, or shrinkage cracks, and weathering along these breaks caused the columns, spires, buttresses, and pinnacles that you see in all directions near you. Forces of erosion have done most of the carving, forming the various rugged features near at hand.

The geological history is very complex and cannot be even summarized in a few paragraphs. Park Rangers can give you additional information regarding the geological history, or explain the origin of features you may wish to know more about.

WHAT TO DO IN BIG BEND NATIONAL PARK

				Approximate Round Trip Time
1.	HIKING TRIPS
	A.	Lost Mine Trail		3 hours
	B.	Juniper Flats		2 hours
	C.	Window Trail		3½ hours
	D.	South Rim Loop Trail		10 hours
2.	HORSEBACK TRAIL TRIPS
	A.	Juniper Flats		2 hours
	B.	Window Trail		3½ hours
	C.	South Rim Loop Trail		9 hours
	D.	Pack Trips by special arrangement.
3.	AUTO TRIPS
	A.	Santa Elena Canyon		4-6 hours
		1.	Visit Mouth of Canyon.
		2.	Castolon trading post.
		3.	Terlingua and Study Butte ghost mining towns (outside park)
	B.	Boquillas Canyon		4-6 hours
		1.	Excellent View of Del Carmen Mountains and Mexican Village of Boquillas.
4.	SUNSETS
	A.	From the Basin through the “Window.”
	B.	Del Carmen from Vicinity of Lower Tornillo and Boquillas.
	C.	Chisos Mountains from vicinity of Lower Tornillo and Boquillas.
	D.	Chisos Mountains from vicinity of Santa Elena Canyon and Study Butte Area.
5.	SUNRISE
	A.	Over Casa Grande from the Basin.
	B.	Over the Del Carmen from vicinity of Hot Springs and Boquillas.
	C.	Over the Chisos Mountains from Santa Elena area.
6.	WILDLIFE
	A.	Over 55 mammals have been identified to date.
	B.	Approximately 200 birds have been identified to date, including the rare Colima warbler and Aplomado falcon.
		Fifty-four reptiles, which include 4 species of turtles, 22 species of lizards, and 28 species of snakes.
7.	WILDFLOWERS, TREES, AND SHRUBS (1,100 plants identified to date)
	A.	Cactuses and other desert flowers are usually at their height of bloom from the latter part of March to the middle of April.
	B.	Semi-desert shrubs—mostly July, August, and early September, depending upon rain.
	C.	Autumn foliage coloring—late November and first half of December.
8.	GEOLOGY
	A.	The oldest rocks (Persimmon Gap) are comparable in age and structure to those found in the Appalachian Mountains.
	B.	The Lowland area is underlain by rock with fossil content, comparable to the Gulf Coast and Great Plains areas.
	C.	Chisos Mountain volcanic area is comparable in age and structure to the great volcanic activity period of the Northwest.