Valles Caldera

The Valles Caldera (or Jemez Caldera) is a 13.7-mile-wide (22.0 km)volcaniccaldera in the Jemez Mountains of northern New Mexico.^[1]Hot springs, streams, fumaroles, natural gas seeps, and volcanic domes dot the caldera landscape.^[5] The highest point in the caldera is Redondo Peak, an 11,254-foot (3,430 m)resurgent lava dome located entirely within the caldera and surrounded by moat-like flows of rhyolitic solidified lavas.^[6] Located within the caldera are several grass valleys, or valles, the largest of which is Valle Grande (locally /ˈvaɪ.eɪˈɡrɑːndeɪ/VY-ay GRAHN-day), the only one accessible by a paved road. In 1975, Valles Caldera was designated as a National Natural Landmark by the National Park Service with much of the caldera being within the Valles Caldera National Preserve, a unit of the National Park System.^[7] The area has a varied history involving cultural significance, economic resources, scientific studies, and complex geological setting.

Use of Valles Caldera dates back to prehistoric times: spear points dating to 11,000 years ago have been discovered.^[8] Several Native American tribes frequented the caldera for hunting prolific game and gathering obsidian that is common in this area. The obsidian was knapped into tools and weapons while wild game was followed and hunted seasonally. Obsidian from the caldera was traded by tribes across much of the Southwest. Eventually, the Spanish, and later Mexican settlers along with the Navajo and other tribes came to the caldera seasonally for grazing livestock. This often resulted in periodic clashes and raids between tribes and cultures. Later, as the United States acquired New Mexico as part of the Treaty of Guadalupe Hidalgo in 1848, the caldera became the backdrop for the Indian wars with the U.S. Army. Around the same time, the caldera and its forests began to be used commercially for ranching and logging.

Baca Ranch

The caldera became part of the Baca Ranch in 1876. The Bacas were a wealthy family given the land as compensation for the termination of a grant given to their family near Las Vegas, in northeastern New Mexico. The family was given four other parcels by the US Government as well, another one in New Mexico, one in Colorado, and two in Arizona. This area, 100,000 acres (40,000 ha), was called Baca Location Number One or Baca Float Number One. Since then, the land has been through a string of exchanges between private owners and business enterprises. It was owned by Frank Bond in the 1930s. Bond, a businessman based in nearby Española, ran up to 30,000 sheep in the caldera, significantly overgrazing the land and causing damage from which the watersheds of the landscape are still recovering.

The land was purchased by the Dunigan family from Abilene, Texas in 1963. Pat Dunigan did not obtain the timber rights and the New Mexico Lumber Company logged the property heavily - removing significant amounts of old-growth douglas fir and ponderosa pine. Dunigan bought out the timber rights in the 1970s and slowed the logging. He negotiated unsuccessfully with the National Park Service and the US Forest Service for possible sale of the property in the 1980s.^[8]

The circular topographic rim of the caldera measures 13.7 miles (22.0 km) in diameter.^[1] The caldera and surrounding volcanic structures are one of the most thoroughly studied caldera complexes in the United States. Research studies have focused on the fundamental processes of magmatism, hydrothermal systems, ore deposition, and glassy rhyolites.^[17] Nearly 40 deep cores have been examined, resulting in extensive subsurface data and geothermal information.

Valles Caldera is the younger of two calderas known at this location, having collapsed over and buried the older Toledo Caldera, which in turn may have collapsed over yet older calderas. The associated Cerros del Rio volcanic field, which forms the eastern Pajarito Plateau and the Caja del Rio, is older than the Toledo Caldera. The Toledo and Valles Calderas formed during eruptions 1.61 million and 1.25 million years ago, respectively.^[18][19] The caldera-forming Toledo eruption emplaced the Otowi member of the Bandelier Tuff 1.61 million years ago, which can be seen along canyon walls west of Valles Caldera, including San Diego Canyon. The younger Tshirege Member of the Bandelier Tuff was formed during the Valles Caldera eruption 1.23 million years ago.^[2] The now eroded and exposed orange-tan, light-colored Bandelier Tuff from these events creates the stunning mesas of the Pajarito Plateau.

كالديرا هي الموقع النموذجي لكالديرا القبة المتجددة ، والتي طُوِّر تكوينها لأول مرة على يد سي إس روس، وآر إل سميث، وآر إيه بيلي خلال أعمال ميدانية في فاليس في ستينيات القرن الماضي. ^{[ 20 ]} استُخدم هذا الموقع النموذجي والدراسات المرتبطة به لدراسة قباب متجددة أخرى حول العالم، بما في ذلك كالديرا يلوستون . بعد الثوران الأولي المُشكِّل للكالديرا في فاليس، ارتفعت قبة ريدوندو بيك المتجددة بدءًا من حوالي 1.2  مليون سنة مضت. ^{[ 2 ]} حدثت ثورات بركانية طفيفة لتدفقات الريوليت في الخندق من حوالي 1.16  مليون سنة مضت في سيرو ديل ميديو إلى 0.07  مليون سنة مضت في بانكو بونيتو، على طول منطقة صدع حلقي بنيوي. ^{[ 21 ] [ 22 ] [ 23 ]} تشكلت صخور الخفاف في إل كاخيتي وصخور الإغنمبريت في باتلشيب روك خلال حدث بركاني واحد قبل 74200 ± 1100 عام، تلاه ثوران تدفق الأوبسيديان في بانكو بونيتو ​​خلال أحدث ثوران بركاني في كالديرا فالييس، قبل 68900 ± 1000 عام. ^{[ 2 ]} لا تزال الكالديرا والمنطقة المحيطة بها تتأثر بالنشاط البركاني المستمر. تُظهر الدراسات الزلزالية وجود منطقة منخفضة السرعة أسفل الكالديرا، مما يشير إلى وجود انصهار جزئي داخل حجرة صهارة متبقية على عمق يتراوح بين 5 و15  كيلومترًا. ^{[ 24 ]} يوجد اليوم نظام حراري أرضي نشط مع ينابيع حارة وفوهات بركانية . ^{[ 1 ]} تقع هذه الكالديرا والهياكل البركانية المرتبطة بها ضمن حقل جيميز البركاني . يقع هذا الحقل البركاني عند ملتقى صدع ريو غراندي ، الذي يمتد من الشمال إلى الجنوب عبر نيو مكسيكو، وخط جيميز ، الذي يمتد من جنوب شرق أريزونا شمال شرقًا إلى غرب أوكلاهوما . ويرتبط النشاط البركاني هنا بالحركات التكتونية لهذا الملتقى. ^{[ 25 ]}

استخدمت وكالة ناسا فوهة البركان في الفترة من أكتوبر إلى نوفمبر 1964، ثم مرة أخرى في سبتمبر 1966، لتدريب رواد فضاء أبولو جيولوجيًا على التعرف على السمات البركانية، مثل تدفقات الرماد البركاني، وشلالات الخفاف، وقباب الريوليت. وكان من بين أبرز المدربين الجيولوجيين روي بيلي. ^{[ 26 ]}

منظر بانورامي لوادي كالديرا، من الحافة الجنوبية الشرقية؛ في المسافة تظهر قمة ريدوندو ( قبة متجددة ) وقبة حمم الريوليت في سيرو لا خارا في أقصى اليسار.

The volcanic properties of Valles Caldera make it a likely source for renewable geothermal energy. Some people oppose the development of geothermal energy, considering it destructive to the scenic beauty, recreational and grazing use. Its impact on the hot springs and supplying aquifers is unknown as experiences from other past geothermal projects proved that production of reservoir fluids had dramatic impacts to the surface thermal features.^[31]

Valles Caldera was home to the first experiments into development of an Enhanced geothermal system (EGS) or Hot-dry-rock (HDR) geothermal system, beginning in 1974 by the Los Alamos National Laboratory at the Fenton Hill reservoir, approximately 3 km west of Valles Caldera. Originally, the Fenton Hill site was chosen as an EGS laboratory in hopes that the proximity to Valles Caldera would increase the temperature of the bedrock, thus requiring shallower drill depths. The abundance of hydrothermal fluids discharged from the nearby caldera resulted in hydrothermal alteration of the rocks at depth, weakening the sealed nature of the reservoir.^[32] The Fenton Hill HDR experiment was finally abandoned in 1998.^[33] The experiments demonstrated that a potential EGS reservoir must be characterized by low permeability, crystalline basement rock with no active faults or joints.^[32]

From 1959 to 1983, approximately 40 exploratory geothermal wells were drilled into the Redondo Creek Graben as part of the Baca geothermal field, a joint operation by the United States Department of Energy and the Union Oil Company of California.^[34] Despite measuring a maximum temperature of 342 °C and having a likely production capacity of 20 MWe, the geothermal field was too small to be economic.^[33][35] Three scientific cores were drilled in Valles Caldera during the mid-1980s as part of the United States Continental Scientific Drilling Program in order to analyze the chemistry of geothermal fluids and the presence of a vapor-dominated cap in the Sulphur Springs region. The maximum bottom hole temperature measured during drilling was 295 °C.^[36] Overall, the geothermal reservoir at Valles Caldera is liquid-dominated rather than vapor-dominated and has a neutral-chloride fluid chemistry with a maximum temperature below 300 °C.^[33]

A number of recreational and/or historical uses take place in Valles Caldera. Many of these uses involve trails. Over two dozen official hiking and biking trails of varying length are available. Maps and trail descriptions may be found in "Hiking Trails in Valles Caldera National Preserve," by Coco Rae. Valles Caldera has many miles of ranch roads, livestock and game trails. These include a network of trails currently designated for horse riding.^[37][38] Historically, Valles Caldera was a location for equestrian endurance races. After establishment of VCNP, the first race in the caldera was held in 2009. The largest grass valley, Valle Grande, is a venue for ski orienteering. Activities are open to the public, though some require reservations. Customer service and concierge services are provided by the Public Lands Interpretive Association. The valley floor is above 8,000 ft (2,400 m) altitude.^[39]

Throughout the caldera, the grass valleys appear groomed: there are few saplings and mature trees lack lower branches. This is due to heavy browsing by elk and cattle and because of frequent grass fires of human and natural origin which kill the lower branches on the Engelmann spruce, Douglas-fir and Ponderosa pine that populate the uplands around the lower-elevation Montane grasslands dominating the bottoms of the calderas. The grasslands were native perennial bunch grass maintained by frequent fire before sheep and cattle grazing. Although the grass appears abundant, it is a limited resource and its growing season is short. Through the VCNP's limited grazing program, it feeds hundreds of cattle in the summer and thousands more of elk in the warm seasons, in drought winters, and during most of the year. The nutritional value of the bunch grasses is considered low or poor quality. Other wildlife that inhabits the area are Golden Eagles, striped Badgers, and the Gunnison Prairie Dog, to name a few.^[40] The National Park Service states that elk population in Valles Caldera is the second largest herd in New Mexico. Hunting is permitted within the National Preserve under certain restrictions and times of the year.^[41][42]

Valles Caldera has provided several filming locations,^[43] most for films in the Western genre. Some of these locations include exterior sets, such as the weathered "ranch house" that can be seen from the highway in Valle Grande, and a small "town".

• 1971 Shoot Out
• 1977 Peter Lundy and the Medicine Hat Stallion (TV)
• 1982 The Gambler (TV)
• 1994 Troublemakers
• 1995 Buffalo Girls (TV)
• 1997 Last Stand at Saber River (TV)
• 2003 The Missing
• 2007 Seraphim Falls^[44]
• 2010 Kites (film) (Hindi/Indian Film)
• 2013 The Lone Ranger
• 2012–2017 Longmire (TV series)^[45]

• Jemez Pueblo, New Mexico
• Valle Vidal

• فريزر جوف، فالس كالديرا: تاريخ جيولوجي . 2009، مطبعة جامعة نيو مكسيكو. ISBN 978-0-8263-4590-5مراجعة مؤرشفة بتاريخ 7 أبريل 2012، في موقع Wayback Machine في مجلة نيو مكسيكو : "بغض النظر عن اهتمامك بـ Valles Caldera، ستتعلم شيئًا جديدًا في كتاب فريزر جوف الجديد."
• كوكو راي، "مسارات المشي في محمية فالي كالديرا الوطنية" . 2020. الدليل الكامل للمسارات في محمية فالي كالديرا الوطنية.

• محمية فالي كالديرا الوطنية ، الموقع الرسمي
• موقع معهد الفيزياء في فالي كالديرا بالبرازيل (باللغة الإنجليزية)
• دليل السفر الجيولوجي من المعهد الجيولوجي الأمريكي
• منظمة كالدرا أكشن ، وهي منظمة مناصرة
• دليل السفر إلى محمية فالي كالديرا الوطنية من ويكي فويج