Normal route
A normal route or normal way is the most used route for ascending and descending a mountain peak. It is the simplest route. In the Alps, routes are classed in the following ways, based on their waymarking and upkeep: Footpaths Hiking trails Mountain trails Alpine routes Climbing routes and High Alpine routes in combined rock and ice terrain, graded by difficultySometimes the normal route is not the easiest ascent to the summit, but just the one, most used. There may be technically easier variations; this is the case on the Watzmannfrau, the Hochkalter and Mount Everest. There may be many reasons these easier options are less well-used: the simplest route is less well known than the normal route; the technically easiest route is more arduous than another and is therefore used on the descent. The technically easiest route carries a much higher risk of e.g. rockfalls or avalanche and is therefore avoided in favour of a more difficult route. The technically easier route requires a complicated or long approach march, or all access may be banned via one country.
The term tourist route may sometimes be applied by those wishing to suggest that other routes up a mountain are somehow more "worthy". This belittling of the "normal route" therefore maintains a distinction between those perceiving themselves as serious mountaineers who disparage the incursion of tourist climbers into their domain
Sierra Nevada (U.S.)
The Sierra Nevada is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies in Nevada; the Sierra Nevada is part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of such ranges that form the western "backbone" of North America, Central America, South America and Antarctica. The Sierra runs 400 miles north-to-south, is 70 miles across east-to-west. Notable Sierra features include the largest alpine lake in North America; the Sierra is home to three national parks, twenty wilderness areas, two national monuments. These areas include Yosemite and Kings Canyon National Parks; the character of the range is shaped by its ecology. More than one hundred million years ago during the Nevadan orogeny, granite formed deep underground; the range started to uplift four million years ago, erosion by glaciers exposed the granite and formed the light-colored mountains and cliffs that make up the range.
The uplift caused a wide range of elevations and climates in the Sierra Nevada, which are reflected by the presence of five life zones. Uplift continues due to faulting caused by tectonic forces, creating spectacular fault block escarpments along the eastern edge of the southern Sierra; the Sierra Nevada has a significant history. The California Gold Rush occurred in the western foothills from 1848 through 1855. Due to inaccessibility, the range was not explored until 1912; the Sierra Nevada lies in Central and Eastern California, with a small but important spur extending into Nevada. West-to-east, the Sierra Nevada's elevation increases from 1,000 feet in the Central Valley to heights of about 14,000 feet at its crest 50–75 miles to the east; the east slope forms the steep Sierra Escarpment. Unlike its surroundings, the range receives a substantial amount of snowfall and precipitation due to orographic lift; the Sierra Nevada's irregular northern boundary stretches from the Susan River and Fredonyer Pass to the North Fork Feather River.
It represents where the granitic bedrock of the Sierra Nevada dives below the southern extent of Cenozoic igneous surface rock from the Cascade Range. It is bounded on the west by California's Central Valley and on the east by the Basin and Range Province; the southern boundary is at Tehachapi Pass. Physiographically, the Sierra is a section of the Cascade-Sierra Mountains province, which in turn is part of the larger Pacific Mountain System physiographic division; the California Geological Survey states that "the northern Sierra boundary is marked where bedrock disappears under the Cenozoic volcanic cover of the Cascade Range." The range is drained on its western slope by the Central Valley watershed, which discharges into the Pacific Ocean at San Francisco. The northern third of the western Sierra is part of the Sacramento River watershed, the middle third is drained by the San Joaquin River; the southern third of the range is drained by the Kings, Kaweah and Kern rivers, which flow into the endorheic basin of Tulare Lake, which overflows into the San Joaquin during wet years.
The eastern slope watershed of the Sierra is much narrower. From north to south, the Susan River flows into intermittent Honey Lake, the Truckee River flows from Lake Tahoe into Pyramid Lake, the Carson River runs into Carson Sink, the Walker River into Walker Lake. Although none of the eastern rivers reach the sea, many of the streams from Mono Lake southwards are diverted into the Los Angeles Aqueduct which provides water to Southern California; the height of the mountains in the Sierra Nevada increases from north to south. Between Fredonyer Pass and Lake Tahoe, the peaks range from 5,000 feet to more than 9,000 feet; the crest near Lake Tahoe is 9,000 feet high, with several peaks approaching the height of Freel Peak. Farther south, the highest peak in Yosemite National Park is Mount Lyell; the Sierra rises to 14,000 feet with Mount Humphreys near Bishop, California. Near Lone Pine, Mount Whitney is at 14,505 feet, the highest point in the contiguous United States. South of Mount Whitney, the elevation of the range dwindles.
The crest elevation is 10,000 feet near Lake Isabella, but south of the lake, the peaks reach to only a modest 8,000 feet. There are several notable geographical features in the Sierra Nevada: Lake Tahoe is a large, clear freshwater lake in the northern Sierra Nevada, with an elevation of 6,225 ft and an area of 191 sq mi. Lake Tahoe lies between a spur of the Sierra. Hetch Hetchy Valley, Yosemite Valley, Kings Canyon, Kern Canyon are examples of many glacially-scoured canyons on the west side of the Sierra. Yosemite National Park is filled with notable features such as waterfalls, granite domes, high mountains and meadows. Groves of Giant Sequoia
Geology of the Yosemite area
The exposed geology of the Yosemite area includes granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a young North American continent; the sediment that formed the area first settled in the waters of a shallow sea, compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were heavily metamorphosed. Most of the rock now exposed in the park is granitic, having been formed 210 to 80 million years ago as igneous diapirs 6 miles below the surface. Over time, most of the overlying rock was uplifted along with the rest of the Sierra Nevada and was removed from the area by erosion; this exposed the granitic rock to much lower pressure, it was subjected to erosion in the forms of exfoliation and mass wasting.
Starting about 3 million years ago a series of glaciations further modified the area by accelerating the erosion. During that time large glaciers periodically filled the canyons. Landslides and river erosion have been the primary erosive forces since the end of the last glacial period, which ended in this area around 12,000 years BP; the area of the park was astride a passive continental margin during the Precambrian and early Paleozoic. Sediment derived from continental sources was deposited in shallow water; the limestones and shales thus created have since been metamorphosed into marble and slate. These rocks are now exposed on isolated pendants in the central parts of the park. Starting in the mid-Paleozoic and lasting into the early Mesozoic, a convergent plate boundary transported many of those seabed sediments into the area of the park. Heat generated from the subduction led to the creation of an island arc of volcanoes on the west coast of Laurentia between the late Devonian and Permian periods.
These rocks were incorporated into proto-North America by the middle of the Triassic, some of them finding their way to the area of the park. Most of these igneous and sedimentary rocks have since been metamorphosed and eroded away. Outcrops of the resulting Shoo Fly Complex and younger Calaveras Complex are now found in the western side of the park. Volcanism in the Jurassic intruded and covered these rocks in what may have been magmatic activity associated with the early stages of the creation of the Sierra Nevada Batholith. 95% of these rocks were removed by uplifted-accelerated erosion. Most of the remaining rocks are exposed as'roof pendants' in the eastern metamorphic zone. Mount Dana and Mount Gibbs are made of these metavolcanic rocks. Only 5% of the rocks exposed in Yosemite National Park are metamorphic; the first phase of regional plutonism started 210 million years ago in the late Triassic and continued throughout the Jurassic to about 150 million years BP. Starting 150 million years ago was an increase in the westward drift rate of the North American Plate.
The resulting orogeny is called the Nevadan orogeny by geologists. The resulting Nevadan mountain range was 15,000 feet high and was made of sections of seafloor and mélange; these rocks were metamorphosed and today can be seen in the gold-bearing metamorphic belt of California's Mother Lode country. In the area of the park these rocks are exposed along the Merced River and State Route 140; this was directly part of the creation of the Sierra Nevada Batholith, the resulting rocks were granitic in composition and emplaced about 6 miles below the surface. The second, major pluton emplacement phase lasted from about 120 million to 80 million years ago during the Cretaceous; this was part of the Sevier orogeny. All told. A few miles of material was eroded away, leaving the Nevadan mountains as a long series of hills a few hundred feet high by 25 million years ago. Starting 20 million years ago and lasting until 5 million years ago a now-extinct extension of Cascade Range volcanoes erupted, bringing large amounts of igneous material in the area.
These igneous deposits blanketed the region north of the Yosemite area. Some lava associated with this activity poured into the Grand Canyon of the Tuolumne and formed Little Devils Postpile. In the late Cenozoic, extensive volcanism occurred east of the park area. Within the Yosemite region, andesitic lava flows and lahars flowed north of the Grand Canyon of the Tuolumne and volcanic dikes and plugs developed from faults on the flanks of Mount Dana. There is evidence for a great deal of rhyolitic ash covering the northern part of the Yosemite region 30 million years ago; this and ash deposits have been completely eroded away. Volcanic activity persisted past 5 million years BP east of the current park borders in the Mono Lake and Long Valley areas; the most significant activity was the creation of the Long Valley Caldera about 700,000 years ago in which about 600 times as much material was erupted than in the 1980 eruption of Mt. Saint Helens; the most recent activity was the
Jim Bridwell
Jim Bridwell was an American rock climber and mountaineer, active since 1965 in Yosemite Valley, but in Patagonia and Alaska. He is noted for pushing the standards of both free climbing and big-wall climbing, alpine climbing, he wrote numerous articles on climbing for leading sport publications. Bridwell is credited with over 100 First Ascents in Yosemite Valley, in addition to conducting the first one-day ascent of The Nose of El Capitan on May 26, 1975 with John Long and Billy Westbay, he founded Yosemite National Park's Search and Rescue Team, spearheaded many rescues that became textbook for search-and-rescue operations. He was a leading force in the changing techniques of climbing and an innovator/inventor of used and copied climbing gear, including copperheads and bird beaks. Jim resided in Palm Desert, California, USA, until his death on February 16, 2018 from complications of hepatitis C, which he had acquired while receiving a tattoo in Borneo during the 1980s. 1965 Entrance Exam, Arch Rock, California, USA with Chuck Pratt, Chris Fredericks and Larry Marshik 1966 Braille Book, Higher Cathedral Rock, California, USA with Chris Fredericks, Joe Faint and Brian Berry.
1967 East Face, Higher Cathedral Rock, California, USA with Chris Fredericks 1967 South Central, Washington Column, California, USA with Joe Faint 1969 Triple Direct, El Capitan, California, USA with Kim Schmitz 1971 Aquarian Wall, El Capitan, California, USA with Kim Schmitz 1971 New Dimensions, Arch Rock, California, USA with Mark Klemens 1971 Nabisco Wall, The Cookie, California, USA 1970 Vain Hope, Ribbon Falls, California, USA with Royal Robbins and Kim Schmitz 1973 Central Pillar of Frenzy, Middle Cathedral Rock, California, USA with Roger Breedlove and Ed Barry 1974 Freestone, Geek Towers, Yosemite Falls, California, USA 1975 Wailing Wall, Tuolumne Meadows, California, USA with Dale Bard and Rick Accomozo 1975 Pacific Ocean Wall, El Capitan, California, USA with Bill Westbay, Jay Fiske and Fred East 1976 Gold Ribbon, Ribbon Falls, California, USA with Mike Graham 1977 Bushido, Half Dome, California, USA with Dale Bard 1978 Sea of Dreams, El Capitan, California, USA with Dale Bard and Dave Diegelman 1978 Zenith, Half Dome, California, USA with Kim Schmitz 1979 Southeast Ridge of Cerro Torre, Argentina with Steven Brewer 1979 Northwest Face, "The Ship Prow" Kichatna Spire, Alaska Range, USA with Andy Embick 1981 Zenyatta Mondatta, El Capitan, California, USA with Peter Mayfield and Charlie Row 1981 Dance of the Woo Li Masters, East Face of The Moose's Tooth, Ruth Gorge, Alaska, USA with Mugs Stump 1982 South Face, "Sapphire Bullets of Pure Love" Pumori, Nepal with Jan Reynolds and Ned Gillette 1987 The Big Chill, Half Dome, California, USA with Peter Mayfield, Sean Plunkett and Steve Bosque 1989 Shadows, Half Dome, California, USA with Charles Row, Cito Kirkpatrick, William Westbay 1991 North Face The Eiger, Bernese Alps, Switzerland 1997 Wyoming Sheep Ranch, El Capitan, California, USA with Giovanni Groaz 1998 Heavy Metal and Tinker Toys, El Capitan, California, USA with Boulos Ayad and Tyson Hausoeffer 1998 Plastic Surgery Disaster, El Capitan, California, USA with Mark Bowling and Giovanni Groaz 1999 The Useless Emotion, The Bear's Tooth, Ruth Glacier, Alaska, USA with Terry Christensen, Glenn Dunmire, Brian Jonas and Brian McCray May 3–21, 1999 1999 Odyssey, Grand Capucin, Mont Blanc, with Giovanni Groaz 1999 Dark Star, El Capitan, California, USA with Giovanni Groaz 2001 The Beast Pillar, The Moose's Tooth, Buckskin Glacier, Alaska, USA with Spencer Pfinsten 2001 Welcome to Afghanistan, El Capitan, California, USA with Giovanni Groaz 2002 Pointless Connection, Yosemite Pointless, California, USA with Giovanni Groaz 2004 Old Guides Variation, El Capitan, California, USA with Jackson Marsten and Giovanni Groaz Bridwell, Jim.
"Brave New World". Mountain. United Kingdom: Ken Wilson. Bridwell, Jim. Climbing Big Walls. Merrillville, IN USA: ICS Books. ISBN 0-934802-59-9. Bridwell, Jim. Largo's Apprenticeship in The Best of Rock & Ice: An Anthology. Seattle WA, USA: The Mountaineers Books. Pp. 102–105. ISBN 0-89886-665-0. Bridwell, Jim. Climbing Adventures: A Climber's Passion. ICS Books. ISBN 978-0934802222. Bridwell, Jim. "The Bear's Tooth: Teaching the new dogs old tricks". American Alpine Journal. New York, NY USA: American Alpine Club. 42: 37–45. ISBN 978-0-930410-87-2. Bridwell, Jim. "Bird's Eye View". Alpinist. Jackson Wyoming, USA: Alpinist Magazine. 18. Retrieved 2008-02-09. Bridwell, Jim. "Giovanni Groaz". The Bird. Translated by Michele Radici. Milan, Italy: Versante Sud s. n. c. p. 303. ISBN 978-88-87890-76-1. Roper, Steve. Climber's Guide to Yosemite Valley. San Francisco, California, USA.: Sierra Club Books. ISBN 978-0-87156-048-3. Reid, Don. Yosemite Climbs: Big Walls. Evergreen, Colorado, USA.: Chockstone Press Press. ISBN 0-934641-54-4.
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Nevada Fall
Nevada Fall is a 594-foot high waterfall on the Merced River in Yosemite National Park, California. It is located below Liberty Cap, at the west end of Little Yosemite Valley; the waterfall is recognized by its "bent" shape, in which the water free-falls for the first third of its length to a steep slick-rock slope. This mid-fall impact of the water on the cliff face creates a turbulent, whitewater appearance in the falls and produces a great deal of mist which covers a wide radius, which led to its current name; the Indian name was Yo-wy-we, signifying the squirm of the falling water. Lafayette Bunnell suggested the name "Nevada" for the waterfall, he wrote, "The Nevada Fall was so called because it was the nearest to the Sierra Nevada, because the name was sufficiently indicative of a wintry companion for our spring... The white, foaming water, as it dashed down Yo-wy-we from the snowy mountains, represented to my mind a vast avalanche of snow."The Emerald Pool forms on the "step" between Nevada Fall and Vernal Fall downstream.
The 317-foot high Vernal Fall is a short hike from the bottom of Nevada Fall. They form a cascade; this cascade is sometimes called the giant staircase, evident when viewed from above, at Glacier Point. The hike to the top of Nevada Fall, along the Mist Trail, is 3 miles from the trailhead in Yosemite Valley. One must first hike to Vernal Fall and trek another 2 miles to reach the top; the John Muir Trail, which starts near the trail to Happy Isles, goes to the top of Nevada Fall. In spite of the dangers and deaths as as June 2013, the pool above Nevada Fall remains a popular swimming location, with no park restrictions. In June 2018, an 18-year-old man fell from the edge of the fall. Media related to Nevada Fall at Wikimedia Commons "Nevada Fall". World Waterfall Database
Royal Robbins
Royal Robbins was one of the pioneers of American rock climbing. After learning to climb at Tahquitz he went on to make first ascents of many big wall routes in Yosemite; as an early proponent of boltless, pitonless clean climbing, he, along with Yvon Chouinard, was instrumental in changing the climbing culture of the late 1960s and early 1970s by encouraging the use and preservation of the natural features of the rock. He went on to become a well-known kayaker. 1957 Northwest Face of Half Dome, Yosemite, CA, USA. First grade VI climb in America. With Mike Sherrick and Jerry Gallwas. 1961 Salathé Wall, El Capitan, Yosemite, CA, USA. Hardest big wall grade VI climb in world at time of first ascent. With Tom Frost and Chuck Pratt. 1962 American Direct, Aiguille du Dru, Mont Blanc Range, France. With Gary Hemming. 1963 Direct NW Face of Half Dome, Yosemite, CA, USA. With Dick McCracken. 1963 Robbins Route, Mount Proboscis, Logan Mountains, NWT, Canada. With Jim McCarthy, Layton Kor and Dick McCracken. 1964 North America Wall, El Capitan, Yosemite, CA, USA.
With Tom Frost, Chuck Pratt and Yvon Chouinard. 1964 North Face, Mount Hooker, Wind River Range, Wyoming, USA. With Dick McCracken and Charlie Raymond. 1964 Danse Macabre, Devils Tower, Wyoming, USA. 1964 Final Exam, Castle Rock, Boulder, CO, USA. With Pat Ament. 1964 Athlete's Feat, Castle Rock, Boulder, CO, USA. 1965 American Direttissima, Aiguille du Dru, Mont Blanc Range, France. With John Harlin. 1967 Nutcracker, Yosemite, CA, USA. An early all-nut protected route, now a Yosemite classic. 1967 West Face, El Capitan, Yosemite Valley - First ascent with TM Herbert. 1967 North Face, VI 5.9 A3, Mount Geikie, Canadian Rockies, first ascent with John Hudson. 1967 North Face, Mount Edith Cavell, Canadian Rockies - First solo ascent. 1968 Muir Wall, El Capitan, Yosemite Valley, CA - First Solo Ascent. 1969 Mount Jeffers, Cathedral Spires, Kichatna Mountains, Alaska, USA. First ascent of peak with Fitschen and Raymond. 1969 The Prow, Washington Column, Yosemite, CA, USA. With Glen Denny. 1969 Tis-sa-ack, Half Dome, Yosemite, CA, USA.
With Don Peterson. 1970 Arcturus, Half Dome, Yosemite, CA, USA. With Dick Dorworth. In 1971, Robbins completed the second ascent, with Don Lauria, of the Dawn Wall on El Capitan, with the intention of erasing the route as they climbed it, their ascent followed the 1970 first ascent by Warren Harding and Dean Caldwell, completed with a heavy-handed reliance on bolts - a method that offended Robbins and other clean climbing advocates. Harding had left all his bolts in the rock. After two pitches, Robbins stopped chopping the bolts because "the quality of the aid climbing was much higher than he had expected of Harding or Caldwell and, of course, it was taking us an awful long time to chop all those goddam bolts." Following his success as a climber, Robbins founded an eponymous outdoor apparel company with his wife Liz Robbins. Royal Robbins, LLC is owned by the New York-based private equity fund Bruckmann, Sherrill & Co.. Liz Robbins rejoined the company in December 2015 as a senior advisor. 1952 Open Book, Tahquitz, CA, USA.
First free ascent. 1960 The Nose, El Capitan, Yosemite, CA, USA. Second ascent. 1963 West Face, Leaning Tower, Yosemite, CA, USA. Second ascent and Yosemite's first wall done solo. 1968 Muir Wall, El Capitan, Yosemite, CA, USA. First Grade VI solo. Robbins authored two seminal books, Basic Rockcraft and Advanced Rockcraft, which emphasized free climbing skills and a clean-climbing ethic. In a section of Advanced Rockcraft called Values, he described his climbing philosophy, he believes that "a first ascent is a creation in the same sense as is a painting or a song", that choosing a climbing line may well be "an act of brilliant creativity". Another creative aspect of a first ascent involves the aids. With modern technology of aid climbing available, a first ascent is more artistic if it consciously rejects the use of certain climbing aids that are not essential to the success of the climb, he places emphasis on using equipment, non-destructive to the mountain environment. He opposes climbs done outside the accepted mores of a given climbing center, or the prevailing style of an area.
He favors what he calls "upward variations", or completing a climb using more stringent standards than used on the first ascent. In Robbins' view, the decision to place a single piton is a matter of "enormous importance" because "like a single word in a poem, it can affect the entire composition". In 1978, Robbins developed psoriatic arthritis, he took up adventure kayaking instead, completing first descents of challenging rivers from high mountain elevations. His early kayaking partners included Doug Tompkins and Reg Lake. In 1980, the three descended the San Joaquin River Gorge from Devil's Postpile to the Mammoth Pool Reservoir, 5000 feet lower and 32 miles away. In 1981, they carried their kayaks over Mount Whitney Pass at 13,777 foot elevation, into Sequoia National Park and descended 55 miles down the Kern Trench. In 1982, joined by Neusom Holmes, they descended the Middle Fork of the Kings River in Kings Canyon National Park, the largest and steepest of these three High Sierra descents.
In 1983, Robbins descended the Tuolumne River in Yosemite National Park from Tuolumne Meadows to Hetch Hetchy Reservoir. He was accompanied by Chuck Stanley, Lars Holbek, John Armstrong and Richard Montgomery, he developed an interest in descending smaller mountain creeks by kayak during their flood stage following heavy
Cretaceous
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, the longest period of the Phanerozoic Eon; the Cretaceous Period is abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas; these oceans and seas were populated with now-extinct marine reptiles and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared; the Cretaceous ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs and large marine reptiles died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras.
The Cretaceous as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin and named for the extensive beds of chalk, found in the upper Cretaceous of Western Europe. The name Cretaceous was derived from Latin creta; the Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use; as with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is defined, being placed at an iridium-rich layer found worldwide, believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico.
This layer has been dated at 66.043 Ma. A 140 Ma age for the Jurassic-Cretaceous boundary instead of the accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences. From youngest to oldest, the subdivisions of the Cretaceous period are: Late Cretaceous Maastrichtian – Campanian – Santonian – Coniacian – Turonian – Cenomanian – Early Cretaceous Albian – Aptian – Barremian – Hauterivian – Valanginian – Berriasian – The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms; the Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type, formed under warm, shallow marine circumstances.
Due to the high sea level, there was extensive space for such sedimentation. Because of the young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide. Chalk is a rock type characteristic for the Cretaceous, it consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas. In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast; the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not consolidated and the Chalk Group still consists of loose sediments in many places; the group has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is a marine system consisting of competent limestone beds or incompetent marls.
Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean. Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half the worlds petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and the Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval; these shales are an important source rock for oil and gas, for example in the subsurface of the North Sea. During th
