The Spring 2021 edition of the Yellowstone Visitor Guide for Yellowstone National Park (NP) in Idaho, Montana and Wyoming. Published by the National Park Service (NPS).
Yellowstone Visitor Guide Spring 2021 National Park Service U.S. Department of the Interior 1st Edition Welcome to Yellowstone National Park YE L L O W S T O N E I S A P L A C E L I K E N O O T H E R . Preserved within its boundaries are Old Faithful and the majority of the world's geysers and hot springs. An outstanding mountain wildland with clean water and air, Yellowstone is home of the grizzly bear and wolf and free-ranging herds of bison and elk. Centuries-old sites and historic buildings that refect the unique heritage of America's frst national park are also protected. Use this visitor guide, combined with the ofcial brochure map and free park app (see page 2), to plan a Yellowstone adventure that is: • SAFE. Yellowstone is very diferent from your home and can be life-threateningly dangerous. Your safety is your responsibility. Read the safety information throughout this guide and take it seriously. • SUCCESSFUL. There is so much to do and see in Yellowstone. Explore things to do on pages 4–7, learn about thermal features and wildlife on pages 8–9, fnd details for developed areas of the park on pages 10–14, and double-check road openings/closures and construction on the back page. • RESPECTFUL. The experiences you have in Yellowstone were made possible by the care of those who came before you. Extend this same courtesy to those who will come after you. Follow all park rules, which are designed to protect both you and the park. The park is assisted in fulflling its mission by its ofcial nonproft partner, Yellowstone Forever. Proceeds from Yellowstone Forever educational bookstores, Institute, and philanthropic eforts support priority park projects and visitor education. Find more information at Yellowstone.org or call (406) 848-2400. Bison graze near Roosevelt Arch at the park's North Entrance. Travel Alerts SEASONAL ROAD OPENING All park roads except the road from the North to Northeast entrances are closed to automobiles through April 15. Weather permitting, park roads will begin opening in stages starting April 16. TOWER TO C ANYON ROAD CLOSED The road between Tower-Roosevelt and Canyon Village is CLOSED all year. MOUNT WASHBURN TR AILS CLOSED All trails to the top of Mount Washburn will be closed. See back page for details COVID-19 Safety Alert The National Park Service follows CDC guidance to reduce the spread of COVID-19. Check locally, on the park website, and in the park app for updates and changes in park operations. Thank you for helping to keep yourself and others safe and healthy. 6 feet 2 meters Mammoth Hot Springs Tower-Roosevelt CLOSED Norris Canyon Village Keep Wildlife Wild Yellowstone is an incredible place to view wildlife. All the large mammals present when Yellowstone became a park in 1872 are here today: grizzly and Wearing a mask is required in all common areas in buildings owned, black bears, wolves, mountain rented, or leased by the National Park Service, including, but not lions, elk, bison, pronghorn, limited to, park visitor centers, administrative ofces, lodges, gift shops, moose, and bighorn sheep. and restaurants. Masks are required outdoors where physical distancing cannot reasonably be maintained. Masks are not required for • Wildlife are dangerous. those under the age of two or when actively eating or drinking. • Do not approach, encircle, follow, or feed any animal. Practice social distancing. Maintain at least 6 feet (1.8 m) of distance • Bison, bears, and elk injure and kill people. between you and others. • Stay at least 100 yards (91 m) from bears and wolves. • Stay at least 25 yards (23 m) from all other animals, including bison and elk. Wash your hands with soap and water for at least 20 seconds, • If an animal moves closer to you, move away or use hand sanitizer. to maintain the appropriate distance. • Do not stop on or block a road. Cover your mouth and nose when you cough or sneeze. • Use pullouts; stay in your car to watch animals. • Store food and trash securely. Backpacks are not secure. If you feel sick, do not visit the park. • Do not feed any animals, even birds and squirrels. r . NATIONA< PARK ;;;: Yellowstone National Park National Park Service U.S. Department of the Interior Emergency Information TTY Park Entrance Radio Dial 911 307-344-7381 307-344-2386 1610 AM Park Tip Line 307-344-2132 To report a crime or criminal activity. Leave as much detail as you can. Remain anonymous, or leave a name and number. Facilities and Services Medical Services Accessibility Yellowstone emergency response A printed guide with accessibility information Cell phone service is very limited in the park and ambulance service is available at visitor centers and on the park and surrounding areas. General cell coverage Call 911 website (go.nps.gov/YELLaccess). areas are shown on the map on the back page Text 911 is not available in Yellowstone. of this guide. Qualifed service animals are welcome Medcor provides medical care, from throughout the park and in all park facilities. Emergency 911 service by cell phone is only emergencies to minor needs, at: However, they must be leashed and under your available in coverage areas. Text 911 is not • Mammoth Clinic control at all times. available in Yellowstone. Year-round During peak hours and periods of heavy visita- 307-344-7965 tion, the cellular network may be very slow. • Lake Clinic NPS Yellowstone National Park App Plan and enrich your visit with the offcial, free NPS ~ Cell Service 5/28–9/19 8:30a–8:30p daily Your provider may or may not roam on networks 307-242-7241 in Yellowstone. • Old Faithful Clinic Yellowstone National Park 5/14–10/1 7a–7p daily As a courtesy to others, silence your mobile App. Digitally explore the 307-545-7325 device while enjoying Yellowstone. world's frst national park—by map or by topic of interest. Discover the natural and Eastern Idaho Regional cultural stories in context with their loca- Medical Center tions. Find the information you need about and other area hospitals visitor centers, events, lodging, places to provide air evacuation eat and shop, and services throughout the Available for free: and trauma care. • Albright Visitor Center Wi-Fi park. Download the app and app con- in Mammoth Hot Springs tent before you begin your adventure, as cell service and Wi-Fi are limited in Data speeds are very limited outside of Yellowstone. Mammoth Hot Springs. Follow @YellowstoneNPS Grizzly bear (Ursus arctos horribilis) near Obsidian Creek in late April. Lodging, Dining, and Tours As one of Yellowstone's offcial concession companies, Yellowstone National Park Lodges offers lodging, dining, camping, and a variety of tours and activities. Visit YellowstoneNationalParkLodges.com for the most up-to-date information, which may change due to COVID-19. For reservations and information, ask at park hotels, or contact Yellowstone National Park Lodges: Phone 307-344-7311, 866-439-7375 TDD 307-344-5395 Online YellowstoneNationalParkLodges.com Email Reserve-YNP@Xanterra.com Mail PO Box 165 Yellowstone, WY 82190 Mammoth Hot Springs Hotel 2 Yellowstone Visitor Guide Safety and Regulations IFE St DL ay froat l m eas be t 1 ar 00 sa y nd ard w s( ol 91 and ve m at l s ) fro eas m a t 25 ll o the yards r an (23 ima m) ls PP IL OT DO N A ! D G AN ER ROACH W Watch Wildlife Safely Store Food Securely Yellowstone ofers wildlife watching opportunities that are unparalleled in the lower 48 states. All the large mammals present when Yellowstone became a park are here today: grizzly and black bears, wolves, mountain lions, elk, bison, pronghorn, moose, and bighorn sheep. You might also see a variety of birds, including bald eagles. Do not feed any wildlife, including small mammals and birds. Eating human food is unhealthy and encourages aggressive behavior. Protect Yourself and the Animals. Obey Park Rules. • Stay at least 100 yards (91 m) from bears and wolves and at least 25 yards (23 m) from all other animals, including bison and elk. • If an animal moves closer to you, move away to maintain the appropriate distance. • Do not surround, crowd, or disrupt any animal's path of movement. Looking for Wildlife? • If other visitors put you or wildlife in danger, leave • To conserve energy, most wildlife are active in the the area and notify a park ranger. cool of dawn or dusk. • Spotlighting—viewing animals with artifcial light— • Animals are everywhere in the park, but it is easier to is illegal. see them in open meadows and sagebrush than in • Calling to attract wildlife is illegal. You may not bugle dense forest. to elk, howl at wolves, or make bird calls of any kind. • Find a place with a broad view for your binoculars or • Tracking wildlife with electronic equipment is not spotting scope, and be prepared to wait. permitted. All food, trash, and scented items must be kept inaccessible to bears at all times. Tents, truck beds, and picnic tables are not secure. In some areas, ravens have learned to unzip packs and scatter the contents. None of these items, even if clean and empty, may be left unattended at any time: • Water and beverage containers • Food, including condiments, even if in containers • Cooking or eating utensils • Cosmetics and toiletries • Stoves and grills • Pet food and bowls • Coolers and ice chests • Pails, buckets, wash basins • Garbage, bagged or not Enjoy watching Yellowstone’s animals but STAY SAFE. They are WILD and DANGEROUS. Other people 2 yards (2 m) Bison, elk, and all other wildlife Bears and wolves 25 yards (23 m) Drones Firearms 100 yards (91 m) Pets Launching, landing, or operating unmanned Firearms are allowed in national parks pursuant to state Pets are not allowed on trails or boardwalks, in the back- aircraft (drones) on lands and waters administered by the and federal regulations. They are prohibited in facilities where country, or in hydrothermal basins. Where allowed, pets must National Park Service is prohibited. signs are posted, such as visitor centers, government offces, and be leashed and remain within 100 feet (30.5 m) of a road or some concession operations. Discharge of frearms is prohibited. parking area. n Lost and Found ? Possession and use of weapons, such as air guns, bows and arrows, spears, and slingshots, is also prohibited. Details are avail- Do not leave a pet unattended, tied to an object, or without able at go.nps.gov/yell-laws. adequate food, water, shade, ventilation, or other basic needs. Call 307-344-5387 to report or retrieve items lost in lodging Owners must bag and dispose of pet waste. We recommend that facilities. In other parts of the park, call 307-344-2109 or look someone in your group remain with your pet at all times to per- online: go.nps.gov/lost-and-found. sonally ensure their well being. Spring 2021 3 Things to Do Camping Yellowstone offers 12 campgrounds with over 2,000 sites. In early spring, Mammoth Campground is the only campground open in the park and is frst-come, frst-served. During the park's busy season, from the beginning of May through the fall, many campsites can be reserved ahead of time. Due to high demand, reservations are highly recommended. First-come, frst-served sites are available during the busy season at Indian Creek, Lewis Lake, and Pebble Creek campgrounds. A campsite at Pebble Creek Campground. No Overfow Camping There are no overfow camping areas available in Yellowstone. No camping or overnight vehicle parking is allowed in pullouts, parking areas, picnic grounds, or any place other than a designated campground. Additional camping may be available in neighboring communities. Check-In and Check-Out Registration desks at Yellowstone National Park Lodges campgrounds are open 7 am to 10 pm during peak season, and 8 am to 9 pm during early and late season. Check-out at reservable campgrounds is 11 am. Length of Stay Camping is limited to 14 days from July 1 through Labor Day (frst Monday in September) and to 30 days the rest of the year. Discounts Holders of Senior and Access passes receive a 50 percent discount on camping fees except at Fishing Bridge RV Park. Quiet Hours From 10 pm to 6 am, no loud audio devices or other noise disturbances are allowed. Group Camping Group camping (tents only) is available at Bridge Bay, Grant, and Madison for organized groups with a designated leader. Fees range from $136 to $399 plus tax and utility fee per night, depending on group size. Advance reservations are required at 307-344-5437 or email@example.com. Food Storage Boxes (see right) Available at each campsite at Indian Creek, Lewis Lake, Mammoth, Norris, Pebble Creek, and Slough Creek campgrounds. Many campsites in other campgrounds are also equipped with bear-proof storage boxes. Food storage box Campgrounds In Order of Opening Reservation Status Dates Rate Sites Elevation (ft/m) Features RV sites Mammoth Winter operations First-come, frst-served Jan 1 – Apr 30 Oct 16 – Dec 31 $25 38 6,200 ft (1,890 m) A, F, G Most are pull-through Mammoth Summer operations All sites reservable recreation.gov May 1 – Oct 15 $25 85 6,200 ft (1,890 m) A, F, G Most are pull-through Madison All sites reservable 307-344-7311 May 14 – Oct 17 $27 * 278 5,800 ft (2,070 m) A, F, DS, G Call for availability Canyon All sites reservable 307-344-7311 May 21 – Sep 19 $32 * 273 7,900 ft (2,410 m) A, F, L, 2S, DS, G Call for availability Bridge Bay All sites reservable 307-344-7311 Jun 11 – Sep 6 $27 * 432 7,800 ft (2,285 m) A, F, DS, G Call for availability Indian Creek First-come, frst-served Jun 11 – Sep 13 $20 70 7,300 ft (2,225 m) A, V 10 sites are 35 ft 35 sites are 30 ft Pebble Creek Some sites reservable recreation.gov Jun 15 – Sep 27 $20 27 6,900 ft (2,100 m) A, V Some long pull-throughs Slough Creek All sites reservable recreation.gov Jun 15 – Oct 12 $20 15 5,260 ft (1,905 m) A, V 14 sites are 30 ft walk frst to assess sites Lewis Lake First-come, frst-served Jun 15 – Nov 7 $20 85 7,800 ft (2,285 m) A, V All sites are 25 ft or less Grant Village All sites reservable 307-344-7311 Jun 18 – Sep 12 $32 * 430 7,800 ft (2,285 m) A, F, L, 2S, DS, G Call for availability Norris CLOSED Fishing Bridge RV Park CLOSED Tower Fall CLOSED 4 Yellowstone Visitor Guide Campground Features * A F V L 2S DS G Rate does not include tax or utility pass-through Accessible sites available Flush toilets Vault toilets Pay laundry onsite Two showers included each night Dump station Generators allowed 8 am to 8 pm Campfres are allowed only in designated grills or rings in park campgrounds, some picnic areas, and specific backcountry campsites. Fully extinguish all campfires—they should be cool to the touch—before leaving them. Things to Do Safely storing items at a backcountry site. Backcountry Camping Overnight backcountry camping is only allowed in designated sites and requires a permit. Detailed information on backcountry permits, fees, and advanced reservations is available online: go.nps.gov/YELLbackcountry. Boating on Yellowstone Lake. Cutthroat trout Fishing Boating Permits are free prior to Memorial Day. General fshing season opens May 29 and closes November 7, 2021. Some areas remain closed until June 15. Fishing permits are required in Yellowstone; state-issued fshing permits are not valid within the park. Anglers 16 years or older need a permit; younger children can fsh for free with a permitted adult. The boating season opens May 29 and closes November 7, 2021. All watercraft (motorized boats, non-motorized boats, and foat tubes) must have a permit and be inspected for aquatic invasive species by park staff. Any watercraft suspected of harboring AIS will be subject to a non-chemical decontamination treatment. From Memorial Day through September 10, a per-person, per-night fee applies: • Backpackers and boaters: $3 per person per night Group maximum $15 per night • Groups with stock animals: $5 per person per night Fishing regulations in Yellowstone protect the unique values of the park ecosystem and conserve native fsh species. Copies of the complete park regulations are available wherever permits are sold and online at go.nps.gov/fsh. Aquatic Invasive Species are nonnative plants and animals that can cause irreversible harm to the ecosystem. New Zealand mudsnails, whirling disease, and lake trout have already resulted in loss of native fsh or closure of some park areas. For current trail conditions visit: go.nps.gov/YELLbackcountryreport. Possession limits and closures vary throughout the park. Anglers are responsible for knowing the regulations in the area they are fshing. Anglers are also responsible for knowing how to tell the diference between species. Native fsh must be released unharmed back into the water immediately. These include: • Arctic grayling • Cutthroat trout • Mountain whitefsh Watercraft users and anglers are asked to inspect all items that may come in contact with park waters, ensuring that they are clean, drained, and dry. Riding the Yellowstone River Trail. Horses, Mules, and Other Stock Animals These tackle and gear restrictions apply: • Hooks must be barbless. • Tackle and lures must be non-toxic. Lead tackle is not allowed. • Bait is prohibited. • Felt-soled footwear is not permitted. Traveling in the Yellowstone backcountry with horses, mules, or llamas is an exciting way to see the park. By their very nature, these large animals have the potential to leave great impacts on the land. Permits are required for both day rides and overnight trips. To get a permit and plan a safe, enjoyable, low-impact trip, contact a backcountry ofce or look online at go.nps.gov/YELLhorseride. • Trails typically open for stock use July 1. Some trails may open earlier or later depending on trail conditions. • Proof of a negative Coggins test is required. • Hay is prohibited in the backcountry, and weedfree hay restrictions are enforced in other areas. • Stock may not be left at trailheads or kept in front-country, drive-in campgrounds overnight. Motorized boating is allowed on Lewis Lake and most of Yellowstone Lake. Only non-motorized boating is allowed on most other lakes. Only one river is open to non-motorized boating: the Lewis River channel between Lewis and Shoshone lakes. If you plan to boat in the park, familiarize yourself with Yellowstone National Park boating regulations and information about inspections and permits, available online at go.nps.gov/YELLboating. BOAT PERMIT AND AIS INSPECTION LOCATIONS Motorized and non-motorized watercraft (including angler foat tubes): • Bridge Bay Ranger Station • Grant Village Backcountry Ofce • Lewis Lake Ranger Station Angler foat tubes only: • Locations listed above • Northeast Entrance Station • Bechler Ranger Station Gardner River below Osprey Falls Swimming For more information, visit go.nps.gov/YELLboating or call 406-581-9040 (Grant AIS inspector) or 406-823-9006 (Lake AIS inspector). Park waters are swift and cold. • Swimming in hot springs or their runoff is prohibited. • Swimming in park rivers is not recommended. Currents can be dangerously strong and fast. • Swimming in Yellowstone lake is not recommended. Average lake temperature is approximately 41°F (5°C). Certain Boats Banned Boats with sealed internal water ballast tanks are temporarily banned in the park to minimize the risk of introducing aquatic invasive species. Spring 2021 5 Things to Do Day Hiking More than 1,000 miles of hiking trails wind through Yellowstone National Park. Whether you hike for half a mile or more than 10, the backcountry can be an escape from the crowds and a chance to get in touch with the wilderness that Yellowstone preserves. Find hikes using the free park app (see page 2) or at go.nps.gov/YELLdayhikes. go.nps.gov/YELLbackcountryreport has information on seasonal closures and trail conditions. Be prepared for wildlife encounters, hike in groups of three or more, and carry bear spray on all hikes. Hiking in Bear Country Hiking in bear habitat has inherent risks. You are likely to be safer if you stay on roads and ofcial trails, but your safety cannot be guaranteed. Federal regulations require you to stay at least 100 yards (91 m) away from bears. Learn more: go.nps.gov/bearspray. Bear spray is available for purchase in Yellowstone where stores are open. Bear spray cannot be taken on airplanes or thrown in the trash. Canisters can be recycled in the park. Check locally or online for locations. • BE ALERT FOR BEARS. • MAKE NOISE in areas with limited visibility. • CARRY BEAR SPRAY, one can with each adult, and know how to use it. • HIKE IN GROUPS of three or more people. • DO NOT RUN; back away slowly. Hiking the Beaver Ponds Trail. Photographers in Lamar Valley Photography Yellowstone is one of the best places in the world to photograph wildlife. The Name of the Game is Patience To get the best shot, you will spend more time waiting and observing than taking photos. Look for patterns in animal behavior that can help you get a great shot. You may have to wait a while, so be ready. Know Your Camera's Limits A cell phone camera will not be able to capture the same resolution and detail as a more advanced standalone camera with large lenses. Good photography isn't about getting close to the animal for a close-up. It's about having the right equipment for the job. 6 Yellowstone Visitor Guide Biking in the spring. Bicycling Stay Safe Behind and in Front of the Camera An unusual vantage point can add drama to your image, but you don't want to add the drama of a hospital visit to your trip. Never sacrifce safety for a photograph. • Be Aware of Your Surroundings Stay behind fences and guard rails. Never turn your back on wild animals. • Keep Children Close to You at All Times Never try to pose them with wildlife. • Stay Out of the Road Do not stop your vehicle in the road or stand in the roadway. Do not block any portion of the road with tripods, chairs, or other objects. Do not block the free fow of trafc. Bicycling, including the use of e-bikes, is permitted on established public roads, parking areas, and designated routes. Bicycles are subject to the same trafc rules as automobiles and are prohibited on trails and boardwalks. Park roads are narrow and winding with few shoulders, so regulations require cyclists to ride single fle, and we strongly recommend wearing a helmet and high-visibility clothing. Smoking Is Prohibited in geyser basins, on trails and boardwalks, in buildings, or within 25 feet (7.6 m) of building entrances. Road elevations range from 5,300 to 8,860 ft (1,615 to 2,700 m), and services and facilities are far apart—typically 20 to 30 miles (37 to 56 km). During April, May, and June, high snowbanks may make travel more dangerous. Find information on the park website at go.nps.gov/YELLbicycling. • Take Only Pictures Removing or possessing natural or cultural resources (like wildfowers, antlers, rocks, and arrowheads) is strictly prohibited. Things to Do Become a Junior Ranger Explore Park Heritage If you're age 4 or older, you can become a Yellowstone Junior Ranger! This program is a way to introduce children—and those young at heart—to the natural wonders of the park as well as their own role in preserving these wonders for the future. Opportunities to connect to the past are everywhere in Yellowstone. Visit Mammoth Hot Springs to walk the self-guiding trail around Fort Yellowstone, which chronicles the US Army's role in protecting the park. Other historic sites include the Norris Museum, Obsidian Clif, and the Old Faithful Inn and Historic District. The Heritage and Research Center (above) is located just beyond the North Entrance in Gardiner, Montana. This facility is home to Yellowstone's museum collection, archives, research library, archeology lab, and herbarium. Open by appointment only. Authorized Guides Many authorized guides and outftters are ready to show you the wonders of Yellowstone, and each has a unique approach. Make sure that your guide, tour company, or other commercial service is fully authorized by the park. Authorized providers are listed on the park website at go.nps.gov/YELLtours. Support Your Park YE. L LOWS,TO INI E FOREVER 1 Yellowstone Forever is the offcial nonproft partner of Yellowstone National Park. Their mission of engagement and support through philanthropy and education for the park will ensure Yellowstone remains for generations to come. Programs about wildlife, plants, geology, and history are perfect for curious adults and families who want to spend a day or more exploring the park with a knowledgeable guide. To learn more, visit Yellowstone.org. Special use permits are required for certain activities including organized gatherings like weddings or church services, public assemblies and demonstrations, some commercial activities like commercial travel, and some types of flming and photography. For more information, call 307-344-2722. Report unauthorized operators to a park ranger, or contact Concessions Management at 307–344–2271. Covered wagons at Yanceys Hole. Make the Most of Your Visit Yellowstone encompasses more than 2.2 million Only one day here? Two or more days? acres, most of it beyond the reach of roads. One could • Drive to the Old Faithful area and walk around the • Explore one theme, such as geology, in depth. For dedicate their entire life to experiencing the park and Upper Geyser Basin. example, visit Mammoth Hot Springs to see traverstill never see it all. Here are suggestions for mak• Visit Old Faithful and one other hydrothermal area, tine formations and view the sedimentary layers of ing the most of the time you do have. like Norris, West Thumb, or Fountain Paint Pots. FolMount Everts, then drive through terrain shaped by low boardwalks and maintained trails to witness hot glaciers to the Tower-Roosevelt area. Tour early in the day to avoid crowds. springs, mudpots, fumaroles, and geysers. • Visit Yellowstone Lake, the largest high-elevation lake Most people tour the park from 10 am to 6 pm. Wild- • Begin in Hayden or Lamar valleys to look for some of in the lower 48 states. Take in the spectacular views life are most active at sunrise and sunset; arriving the park's large animals. Bring binoculars or a spotof West Thumb and the Absaroka Mountains from its before 8 am improves your chances of observing aniting scope, and enjoy animals from a safe distance. shores. Explore the hot springs, mud pots, and geymals during their active periods. Park entrance gates • For a break from the road, consider one or two modsers of West Thumb Geyser Basin. Hike one of the are open 24 hours a day. erate day hikes. Always carry rain gear, extra food local trails, such as the Scenic Lake Overlook near and water, bear spray, and other emergency equipWest Thumb. Visit a hidden gem. ment when venturing into the backcountry. • Slow down and try your hand at capturing the beauty Take a day hike, or stroll one of our historic walking • Have a picnic. Unpack your basket at any of the 51 of Yellowstone through journaling, painting, or simtours at Fort Yellowstone or Old Faithful. Explore picnic areas throughout the park. ply observing. nearby national park units, national forests, state forests, and state parks. The region ofers a variety of public lands for recreation and enjoyment. Spring 2021 7 Famously Hot Features Yellowstone was established in 1872 as the world's frst national park primarily because of its unparalleled collection of geysers, hot springs, mudpots, and steam vents. Stay on Boardwalks and designated trails. Do not touch any thermal features, and keep foreign objects out of springs. It can be windy, so cinch your hats, and secure your items. Fumaroles, or steam vents, are the hottest hydrothermal features in the park. They are easier to see in cool weather. Geysers erupt with steaming hot water. Variations in each geyser's underground reservoir determine whether it is regular and predictable—like Daisy Geyser in the Upper Geyser Basin—or irregular like Steamboat Geyser in Norris Geyser Basin. Hot springs are the most common hydrothermal features in the park. They vary from frothing mochalike boiling water to clear and calm pools of tremendous depth. Mudpots are acidic features with a limited water supply. Their consistency and activity vary with the seasons and precipitation. Travertine terraces are found at Mammoth Hot Springs, where the interactions of water and limestone create chalk-white travertine. Norris Geyser Basin How Faithful is Old Faithful? How do geysers work? Some Like It Hot Since its frst documentation in 1870, Old Faithful has been one of the more predictable geysers. Over time, the average interval between Old Faithful's eruptions has increased or decreased due to changes in its plumbing from ongoing processes and earthquakes. The Hebgen Lake Earthquake (1959) caused an increase in the time between eruptions. Descendants of the frst life forms to evolve on Earth live in the extremely hot, sometimes acidic, habitats in and around hydrothermal features. The heat-loving microorganisms, called thermophiles, survive and thrive in Yellowstone's active volcanic environment. The average interval between eruptions at Old Faithful Geyser is 94 minutes ± 10 minutes, with intervals ranging from 54 to 114 minutes. Geysers are hot springs with narrow spaces in their plumbing, usually near the surface. These constrictions prevent water from circulating freely to the surface where heat would escape. The deepest circulating water can be more than twice as hot as the surface boiling point of 199°F (93°C). The surrounding pressure also increases with depth, similar to the ocean. Increased pressure exerted by the enormous weight of the overlying rock and water prevents the water from boiling as it heats up. As the water rises, steam forms. Bubbling upward, steam expands as it nears the top of the water column until the bubbles are too large and numerous to pass freely through the constrictions. At a critical point, the confned bubbles actually lift the water above, causing the geyser to splash or overfow. This decreases pressure on the system, and violent boiling results. Tremendous amounts of steam force water out of the vent, and the eruption begins. 8 Yellowstone Visitor Guide Nourished by energy and chemical building blocks available in the hot springs, the microbes build vividly-colored communities like those you see in the photo above. The colors vary depending on the types of microbes, the pH (acidity or alkalinity), temperature of the feature, and exposure to sunlight. Millions of individual microbes can connect into long strands called flaments. Some flaments tangle, forming mats. Flowing water brings other microbes, organic matter, and minerals that add to the mat. Mats can be thin as tissue paper or thick as lasagna. Because of their fragility, they must not be touched. Water is expelled faster than it can enter the geyser's plumbing system, and the heat and pressure gradually decrease. The eruption stops when the water reservoir is exhausted or when the system cools. Dozens of types of microbes from all three domains of life can exist in these mats, from Archea in the hottest, most acidic features to the more widespread Bacteria and Eukarya. Yellowstone's geyser basins contain fountain- and cone-type geysers. Fountain-type geysers shoot water in various directions from a pool of water. Cone-type geysers like Old Faithful erupt in a concentrated jet of water from inside a rock formation. Scientists continue to study the many mysteries of thermophiles and their extreme habitats in the living laboratories of Yellowstone's thermal areas and features. Wild Lands and Wildlife Wolves in Yellowstone