Big Bend National Park in the U.S. state of Texas has national significance as the largest protected area of Chihuahuan Desert topography and ecology in the United States. It contains more than 1,200 species of plants, more than 450 species of birds, 56 species of reptiles, and 75 species of mammals. [4]

The national park covers 801,163 acres (324,219 ha). [2] A variety of Cretaceous and Cenozoic fossil organisms exist in abundance, and the park has artifacts estimated to be 9,000 years old. Historic buildings and landscapes offer graphic illustration of life along the international border in the 19th century.

For more than 1,000 miles (1,600 km), the Rio Grande/Río Bravo forms the international boundary between Mexico and the United States, and Big Bend National Park administers approximately 118 miles (190 km) along that boundary. The park was named after the area, which is bounded by a large bend in the river, and Texas-Mexico border ( see map at right below ).

Because the Rio Grande serves as an international boundary, the park faces unusual constraints while administering and enforcing park rules, regulations, and policies. In accordance with the Treaty of Guadalupe Hidalgo, the park's territory extends only to the center of the deepest river channel as the river flowed in 1848. The rest of the land south of that channel, and the river, lies within Mexican territory. The park is bordered by the protected areas of Parque Nacional Cañon de Santa Elena and Maderas del Carmen in Mexico.

Geography and climate

The park exhibits dramatic contrasts and its climate may be characterized as one of extremes. Dry and hot late spring and summer days often exceed 100 °F (38 °C) in the lower elevations. Winters are normally mild but subfreezing temperatures occasionally occur. Because of the range in altitude from about 1,800 feet (550 m) along the river to Emory Peak in the Chisos Mountains at 7,832 feet (2,387 m), [4] a wide variation in available moisture and temperature exists throughout the park. These variations contribute to an exceptional diversity in plant and animal habitats. Some species in the park, such as the Chisos oak ( Quercus gravesii ), are found nowhere else in the United States.

The 118 mi (190 km) of river that form the southern park boundary include the spectacular canyons of Santa Elena, Mariscal, and Boquillas. The Rio Grande, which meanders through this portion of the Chihuahuan Desert, has cut deep canyons with nearly vertical walls through three uplifts made primarily of limestone. Throughout the open desert areas, the highly productive Rio Grande riparian zone includes numerous plant and animal species and significant cultural resources. The vegetative belt extends into the desert along creeks and arroyos.

South of the border lie the Mexican states of Chihuahua and Coahuila and newly protected areas for flora and fauna, which are regions known as the Maderas del Carmen and the Cañón de Santa Elena.

In 2012, the park was named as an international dark-sky park by the International Dark-Sky Association, which recognized the park as one of only ten places in the world certified for dark-sky stargazing. In addition, the association recognized the park as having the darkest measured skies in the lower 48 United States. On many nights, park visitors can look up to the night's sky to see thousands of stars, bright planets, and the clear outline of the Milky Way band. Astronomers, both professional and amateur, are seen on many moonless nights gazing up at the stars through portable telescopes.

Climate data for Castolon weather station, Texas. (Elevation 2,170ft)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 90
(32)
97
(36)
105
(41)
109
(43)
115
(46)
117
(47)
115
(46)
114
(46)
110
(43)
105
(41)
99
(37)
90
(32)
117
(47)
Average high °F (°C) 68.2
(20.1)
74.4
(23.6)
82.9
(28.3)
91.9
(33.3)
99.8
(37.7)
103.4
(39.7)
102.2
(39)
101.1
(38.4)
96.3
(35.7)
88.5
(31.4)
77.7
(25.4)
68.4
(20.2)
87.9
(31.1)
Average low °F (°C) 34.5
(1.4)
39.5
(4.2)
47.1
(8.4)
56.2
(13.4)
66.2
(19)
73.1
(22.8)
74.4
(23.6)
73.5
(23.1)
68.6
(20.3)
57.7
(14.3)
44.2
(6.8)
35.4
(1.9)
51.7
(10.9)
Record low °F (°C) 7
(−14)
5
(−15)
22
(−6)
28
(−2)
44
(7)
42
(6)
60
(16)
64
(18)
47
(8)
29
(−2)
21
(−6)
7
(−14)
5
(−15)
Average precipitation inches (mm) 0.37
(9.4)
0.29
(7.4)
0.23
(5.8)
0.41
(10.4)
0.96
(24.4)
1.45
(36.8)
1.71
(43.4)
1.62
(41.1)
1.47
(37.3)
1.06
(26.9)
0.36
(9.1)
0.30
(7.6)
10.24
(260.1)
Source: The Western Regional Climate Center [5]
Climate data for Chisos Basin weather station, Texas. (Elevation 5,300ft)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 82
(28)
84
(29)
96
(36)
96
(36)
99
(37)
103
(39)
102
(39)
99
(37)
97
(36)
94
(34)
89
(32)
87
(31)
103
(39)
Average high °F (°C) 58.3
(14.6)
61.8
(16.6)
68.7
(20.4)
76.3
(24.6)
82.8
(28.2)
86.8
(30.4)
84.8
(29.3)
83.7
(28.7)
79.5
(26.4)
73.8
(23.2)
65.2
(18.4)
59.4
(15.2)
73.4
(23)
Average low °F (°C) 36.9
(2.7)
39.1
(3.9)
44.1
(6.7)
51.5
(10.8)
58.5
(14.7)
63.3
(17.4)
63.7
(17.6)
62.7
(17.1)
58.6
(14.8)
51.9
(11.1)
43.2
(6.2)
37.9
(3.3)
51.0
(10.6)
Record low °F (°C) −3
(−19)
1
(−17)
12
(−11)
25
(−4)
37
(3)
45
(7)
53
(12)
52
(11)
34
(1)
19
(−7)
13
(−11)
4
(−16)
−3
(−19)
Average precipitation inches (mm) 0.68
(17.3)
0.58
(14.7)
0.41
(10.4)
0.62
(15.7)
1.59
(40.4)
2.21
(56.1)
3.39
(86.1)
3.12
(79.2)
2.48
(63)
1.51
(38.4)
0.57
(14.5)
0.51
(13)
17.67
(448.8)
Source: The Western Regional Climate Center [6]

Geology

The oldest recorded tectonic activity in the park is related to the Paleozoic Marathon orogeny, although Proterozoic events (over 550 Mya) possibly have some deep control. The Marathon orogeny (part of the Ouachita-Marathon-Sonora orogenic belt) is part of thrusting of rocks from the South American Plate over the North American Plate. This can be best seen in the Persimmon Gap area of the park. This orogenic event is linked to the lack of Triassic - and Jurassic -age rocks in the park. [4]

Between the Triassic and the Cretaceous, the South American Plate rifted from the North American Plate, resulting in the deposition of the Glen Rose Limestone, Del Carmen Limestone, Sue Peaks Formation, Santa Elena Limestone, Del Rio Clay, Buda Limestone, and Boquillas formations (preserved in the Sierra del Carmen–Santiago Mountains, Nine Point Mesa, Mariscal Mountain, and Mesa de Anguila areas). Also during this time, the Chihuahua trough formed as the Gulf of Mexico opened, which resulted in east-west striking normal faulting. [4] As a result of this depositional time, dinosaur, [7] forest [8] [9] and other fossils are preserved in the park.

Following the ending of rifting in the Late Cretaceous to the early Cenozoic, the Big Bend area was subjected to the Laramide orogeny. This period of (now east-west) compression caused the northeast-facing Mesa de Anguila (an uplifted monocline on the southwest margin of the park), the southwest-facing Sierra del Carmen–Santiago Mountains (an uplifted and thrust-faulted monocline that forms the boundary of the park on the east) and the Tornillo Basin. During the middle Cenozoic, most of the volcanic rocks, including the Chisos group, the Pine Canyon caldera complex, and the Burro Mesa Formation, formed. [4]

The most recent tectonic activity in the park is basin and range faulting from the Neogene to Quaternary. This period of east-west extension has resulted in Estufa and Dehalo bolsons in the Chisos Mountains, as well as the Terlingua and Sierra del Carmen, Chalk Draw, and Burro Mesa faults. The Rio Grande has entered the Big Bend area roughly 2 Mya, and since then, extensive erosion and downcutting have occurred. [4]