Saguaro National Park Informations

Saguaro National Park is an American national park in Pima County, southeastern Arizona. The 92,000-acre (37,000 ha) park consists of two separate areas—the Tucson Mountain District (TMD) about 10 miles (16 km) west of the city of Tucson and the Rincon Mountain District (RMD) about 10 miles (16 km) east of the city—that preserve Sonoran Desert landscapes, fauna, and flora, including the giant saguaro cactus.

The volcanic rocks on the surface of the Tucson Mountain District differ greatly from the surface rocks of the Rincon Mountain District; over the past 30 million years, crustal stretching displaced rocks from beneath the Tucson Mountains of the Tucson Mountain District to form the Rincon Mountains of the Rincon Mountain District. Uplifted, domed, and eroded, the Rincon Mountains are significantly higher and wetter than the Tucson Mountains. The Rincons, as one of the Madrean Sky Islands between the southern Rocky Mountains and the Sierra Madre Oriental in Mexico, support high biodiversity and are home to many plants and animals that do not live in the Tucson Mountain District.

Earlier residents of and visitors to the lands in and around the park before its creation included the Hohokam, Sobaipuri, Tohono O'odham, Apaches, Spanish explorers, missionaries, miners, homesteaders, and ranchers. In 1933, President Herbert Hoover, using the power of the Antiquities Act, established the original park, Saguaro National Monument, in the Rincon Mountains. In 1961, President John F. Kennedy added the Tucson Mountain District to the monument and renamed the original tract the Rincon Mountain District. Congress combined the Tucson Mountain District and the Rincon Mountain District to form the national park in 1994.

Popular activities in the park include hiking on its 165 miles (266 km) of trails and sightseeing along paved roads near its two visitor centers. Both districts allow bicycling and horseback riding on selected roads and trails. The Rincon Mountain District offers limited wilderness camping, but there is no overnight camping in the Tucson Mountain District.

The park gets its name from the saguaro (Carnegiea gigantea), a large cactus that is native to the Sonoran Desert and that does not grow naturally elsewhere.Rincón—as in Rincon Mountains, Rincon Creek, and Rincon Valley—is Spanish for corner, and refers to the shape of the mountain range and its footprint. The name Tucson derives from Papago-Piman words cuk ṣon [ˡtʃukʂɔn], meaning dark spring or brown spring.Tank or Tanque refers to a small artificial pool behind a dam that traps runoff in an existing natural depression.Madrean derives from Madre in Sierra Madre (Mother Mountains).

The park consists of two separate parcels, the Tucson Mountain District (TMD) to the west of Tucson, Arizona, and the Rincon Mountain District (RMD) to the east. Each parcel comes within about 10 miles (16 km) of the center of the city. Their total combined area in 2016 was 91,716 acres (37,116 ha). The Tucson Mountain District covers about 25,000 acres (10,000 ha), while the much larger Rincon Mountain District accounts for the balance of about 67,000 acres (27,000 ha). About 71,000 acres (29,000 ha) of the park, including large fractions of both districts, is designated wilderness.

Interstate 10, the major highway nearest to the park, passes through Tucson. Tucson Mountain Park abuts the south side of the Tucson Mountain District, and to its west lies the Avra Valley. The Rincon Mountain Wilderness, a separate protected area of about 37,000 acres (15,000 ha) in the Coronado National Forest, abuts the Rincon Mountain District on the east and southeast, while the Rincon Valley lies immediately south of the western part of the Rincon Mountain District.

Both districts conserve tracts of the Sonoran Desert, including ranges of significant hills, the Tucson Mountains in the west and the Rincon Mountains in the east. Elevations in the Tucson Mountain District range from 2,180 to 4,687 feet (664 to 1,429 m), the summit of Wasson Peak. Elevations within the Rincon Mountain District vary from 2,670 to 8,666 feet (814 to 2,641 m) at the summit of Mica Mountain.

Saguaro National Park lies within the watershed of the north-flowing Santa Cruz River, which is generally dry. Rincon Creek in the southern part of the Rincon Mountain District, free-flowing for at least part of the year, has the largest riparian zone in the park. The creek is a tributary of Pantano Wash, which crosses Tucson from southeast to northwest to meet Tanque Verde Wash. The two washes form the Rillito River, another dry wash, an east–west tributary of the Santa Cruz River. The washes in both districts are usually dry but are subject at times to flash floods. Smaller riparian zones are found near springs and tinajas in the Rincon Mountain District. The largest of the springs is at Manning Camp, high in the Rincons.

According to the Köppen climate classification system, Saguaro National Park has a Hot semi-arid climate (BSh). According to the United States Department of Agriculture, the Plant Hardiness zone at Red Hills Visitor Center 2,553 feet (778 m) is 9b with an average annual extreme minimum temperature of 25.8 °F (−3.4 °C), and 9a with an average annual extreme minimum temperature of 23.4 °F (−4.8 °C) at Rincon Mountain Visitor Center 3,091 feet (942 m).

Brief violent summer rains are sometimes accompanied by lightning, dust storms and flash floods. Some moisture at the highest elevations in the Rincons falls as snow in winter; snowmelt adds to the limited water available at lower elevations later in the year.

Studies of the effects of climate change on the park show that its annual mean temperature rose about 4 °F (−16 °C) from 1900 to 2010.

Saguaro National Park's oldest rocks, the Pinal Schist, pre-date the formation of the contemporary Basin and Range Province, of which the park is a part, by about 1.7 billion years. The schist is exposed in the Rincon Mountain District along a dry wash off Cactus Forest Loop Drive. Other ancient rocks, 1.4-billion-year-old altered granites, form much of Tanque Verde Ridge in the Rincon Mountain District.

Much later, about 600 million years ago, shallow seas covered the region around present-day Tucson; over time that led to deposition of sedimentary rocks—limestones, sandstones, and shales. Limestone, which occurs in the park in several places, was mined here in the late 19th century to make mortar. The future park land had six lime kilns, two in the Tucson Mountain District, and four in the Rincon Mountain District. Three, all in the Rincon Mountain District, can be visited today—two along the Cactus Forest Trail and one along the Ruiz Trail.

About 80 million years ago tectonic plate movements induced a period of mountain building, the Laramide orogeny, which lasted until about 50 million years ago in western North America. Explosive volcanic eruptions formed the Tucson Mountains about 70 million years ago, and the roof of the volcano at their center collapsed to form a caldera 12 miles (19 km) across. The caldera was eventually filled by debris flows, the intrusion of a granitic pluton, and lava flows, some as recent as 30 to 15 million years ago. Volcanic rocks exposed in and near the Tucson Mountain District are remnants of these events. Examples include large breccia exposed at Grants Pass and a granitic remnant of the magma chamber, which is visible from the Sus Picnic Area in the Tucson Mountain District. Not all of the molten granite reached the surface of the Tucson Mountains; some cooled and crystallized far below.

The Tucson Basin and nearby mountains—including the Tucson Mountains to the west, the Santa Catalinas to the north, and the Rincons to the east—are part of the Basin and Range Province extending from northern Mexico to southern Oregon in the United States. The province, of relatively recent geologic origin, formed when plate movements stretched and thinned the Earth's crust in this part of western North America until the crust pulled apart along faults. The Catalina Fault, a low-angle detachment fault, began to form about 30 million years ago about 6 to 8 miles (10 to 13 km) below the surface of the Tucson Mountains. The rocks under the fault, the lower-plate rocks, were eventually displaced 16 to 22 miles (26 to 35 km) east-northeast relative to the rocks above the fault, then uplifted, domed, and eroded to form the Santa Catalina and Rincon mountains visible today. Although the volcanic rocks seen on the surface of the Tucson Mountain District are not found in the Rincon Mountain District, the crystallized granite (Catalina gneiss) from beneath the Tucson Mountains was eventually exposed on the Rincon Mountain District's surface. The most common rock type in the Rincon Mountains, this banded gneiss is visible in the Rincon Mountain District at sites such as Javelina Rocks along the Cactus Forest Loop Drive.

The earliest known residents of the land in and around what later became Saguaro National Park were the Hohokam, who lived there in villages between 200 and 1450 A.D. Petroglyphs and bits of broken pottery are among Hohokam artifacts found in the park. The Hohokam hunted deer and other animals, gathered cholla buds, prickly pears, palo verde pods, and saguaro fruit, and grew corn, beans, and squash. Subsequent indigenous cultures, the Sobaipuri of the Tucson Basin and the Tohono O'odham to the west, may be descendants of the Hohokam, though the evidence is inconclusive.

Spanish explorers first entered Arizona in 1539–40. Non-native settlement of the region near the park did not occur until 1692 with the founding of San Xavier Mission along the Santa Cruz River, which flowed through Tucson. In 1775, the Spaniards built Presidio San Agustín del Tucsón, a military fort in what was then part of New Spain, in part to protect against raids by Apaches.

The lands that eventually would become Saguaro National Park remained relatively free of development until the mid-19th century, after Arizona had become part of the United States. After passage of the Homestead Act of 1862, the arrival of the railroad in 1880, and the end of the Apache Wars in 1886, homesteaders and ranchers established themselves in the Tucson and Rincon Mountains, and miners sought silver, copper, and other valuable ores and minerals. Mining in the park continued intermittently through 1942, while ranching on private in-holdings within the park continued until the mid-1970s.

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