Boreal (period)
In paleoclimatology
Paleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...

 of the Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

, the Boreal was the first of the Blytt-Sernander
The Blytt-Sernander classification, or sequence, is a series of north European climatic periods or phases based on the study of Danish peat bogs by Axel Blytt and Rutger Sernander...

 sequence of north European climatic phases that were originally based on the study of Danish peat bogs, named for Axel Blytt and Rutger Sernander, who first established the sequence. In peat bog sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

s, the Boreal is also recognized by its characteristic pollen zone
Pollen zone
Pollen zones are a system of subdividing the last glacial period and Holocene paleoclimate using the data from pollen cores. The sequence provides a global chronological structure to a wide variety of scientists, such as geologists, climatologisists, geographists and archaeologists, who study the...

. It was preceded by the Younger Dryas
Younger Dryas
The Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief period of cold climatic conditions and drought between approximately 12.8 and 11.5 ka BP, or 12,800 and 11,500 years before present...

, the last cold snap of the Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, and followed by the Atlantic
Atlantic (period)
The Atlantic in palaeoclimatology was the warmest and moistest Blytt-Sernander period, pollen zone and chronozone of Holocene northern Europe. The climate was generally warmer than today. It was preceded by the Boreal, with a climate similar to today’s, and was followed by the Sub-Boreal, a...

, a warmer and moister period than our most recent climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

. The Boreal, transitional between the two periods, varied a great deal, at times comprising within it climates like today's.

Subdividing the Boreal

Subsequent to the original Blytt-Sernander scheme, the first stage of the Boreal was divided off as a Pre-boreal transitional phase, followed by the Boreal proper. Some current schemes based on pollen zones also distinguish a pre-Boreal (pollen zone IV), an early Boreal (pollen zone V) and a late Boreal (pollen zone VIa, b, and c).


The generally accepted date for the end of the Younger Dryas
Younger Dryas
The Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief period of cold climatic conditions and drought between approximately 12.8 and 11.5 ka BP, or 12,800 and 11,500 years before present...

 and the start of the Pre-Boreal is 11,500 Before Present
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...

 calibrated. The start of the period is relatively sharply defined by a rise of 7 °C in 50 years. The date is based fairly solidly on Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

 ice core
Ice core
An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere. As the ice forms from the incremental build up of annual layers of snow, lower layers are older than upper, and an ice...

s, which give 11,640 BP for the late Younger Dryas and 11,400 BP for the early Pre-Boreal.

But estimates of other dates vary by up to 1000 years, for a number of reasons. First, "Boreal" can identify a paleoclimate, a pollen zone or a temporally-fixed chronozone, and those three bases of definition allow quite different dates. Second, different dating methods obtain different dates. The underlying problem is that climate and pollen vary somewhat from region to region. The scientists of each region use the methods available in their region, whether lake varves, the annual layers of sediment from ancient or modern lake bottoms, ice cores or counts of tree rings (dendrochronology
Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year...


Standardization has become of increasing concern to scientists everywhere. Dates from many methods continue to multiply as paleoclimatologists seek higher resolution. But it is unclear whether regional variation will allow high-resolution standardization.

Yet, there are some solid dates of the PreBoreal and Boreal. The Saksunarvatn tephra
Saksunarvatn tephra
In the science of tephrochronology, the Saksunarvatn tephra is volcanic ejecta that formed an ash layer that is useful in dating Northern European sediment layers that were laid down during the Boreal period, the warm climate phase that followed the cold snap of the Younger Dryas as the earth made...

 (an ash layer of volcanic fall-out), is dated in Greenland ice to 10,180±60 BP; in lake deposits at Krakenes in Norway, to 10,010–9,980 years BP calibrated; in northwest German lakes, to 10,090 BP calibrated. The tephra occurs in early Boreal contexts. So, it seems certain that the early Boreal (pollen zone V) includes the year 10,000 BP. Similarly, the late Boreal includes the Kilian/Vasset tephra of Swiss and southwest German lakes at 8200 BP, all calibrated. But the borders are less certain.

Studies of bog
A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....

s in northwest Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 are the basis for a division of the PreBoreal (PB) into PB-1, 10,000-9800, and PB-2, 9800–9300 BP incal. The scheme goes on to divide the Boreal (BO) into BO-1, 9300–9000, BO-2, 9000–8500, and BO-3, 8500–8000, incal. CalPal used on these dates suggests overall boundaries of 11,500 and 10,500 BP for the Pre-Boreal, and the end of the Boreal at 8900.

Dates given recently are usually earlier than those given more than 10 years ago. For example, Iverson (1973) and Rud (1979) give dates of 10,000–9000 BP for the PreBoreal and 9000–8000 BP for the Boreal, which are incalibrated C-14 dates based on Scandinavian pollen stratigraphy.

Presumably, more-recent dates are more accurate, as technology improves with time, often quite rapidly. Yet, pollen and climate phases also to some degree may depend on latitude, so no date can be regarded as certainly wrong. Scientists look for the overall pattern of the dates, but that technique is not 100% reliable, either.


Before the Pre-Boreal, Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

 was locked in the chill of the Younger Dryas and was a mostly continuous tundra
In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...

 belt, with regions of taiga
Taiga , also known as the boreal forest, is a biome characterized by coniferous forests.Taiga is the world's largest terrestrial biome. In North America it covers most of inland Canada and Alaska as well as parts of the extreme northern continental United States and is known as the Northwoods...

, covered with a blanket of grasses, shrubs and other low plants typical of open land. Large numbers of herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s wandered in herds over vast distances. The blanket teemed with small, rapidly reproducing species, which supported food chains of larger predators. The largest predators and humans hunted the mammals of the open tundra.

The Pre-Boreal began with a sudden rise in temperature that abruptly changed this ecosystem. Forest replaced the open lands in Europe, and forest-dwelling animals spread from southern refugia
In biology a refugium , sometimes termed simply a refuge, is a location of an isolated or relict population of a once more widespread species. This isolation can be due to climatic changes, geography, or human activities such as deforestation and over-hunting...

 and replaced the ice-age tundra mammals; new climax ecosystems developed. The old fauna persisted in Central Asia, but were soon hunted out, as they were not replenished by the larger areas formerly nourishing the ecosystem.

The sea brought additional isolation by rising rapidly and drowning the entire coast. Ireland was cut off early in the Boreal, suffering an impoverishment of species. It is home to only two-thirds of the species present in Britain. Britain was cut off by the end of the Boreal. Forest had closed over the former European tundra.

Humans had to adapt to the encroaching forest or move east with the large mammals. Those who stayed became hunter-gatherers of the forests and fishers of the numerous bays, inlets and shallow waters around the thousands of islands that now spangled the seas of Europe. They lived richly and were encouraged to enter the pre-productive phase that we call the Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....

. Those who moved east hunted out the last of wild big game and turned their best efforts into learning to herd what was left. In the Americas, humans had left the Paleoindian phase and were now in the Archaic.

Meanwhile humanity toward the south of the north temperate zone had already turned to food production in a number of widely separated locations and were on the brink of civilization. There is no evidence of any extensive contact with the cultures of the north during the Boreal. The producers tended to live in dense centers without any interest in moving from there except when motivated to find new lands. The gatherers ranged widely over their lands, building only temporary settlements in which to spend the winter.


During the Pre-Boreal pollen zone IV, large quantities of tree pollen began to replace the pollen of open-land species, as the most mobile and flexible arboreal species colonized their way northward, replacing the ice-age tundra plants. Foremost among them were the birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...

es, Betula pubescens and Betula pendula, accompanied by Sorbus aucuparia
Sorbus aucuparia
Sorbus aucuparia , is a species of the genus Sorbus, native to most of Europe except for the far south, and northern Asia...

and Quaking Aspen, Populus tremula
Populus section Populus, of the Populus genus, includes the aspen trees and the white poplar Populus alba. The five typical aspens are all native to cold regions with cool summers, in the north of the Northern Hemisphere, extending south at high altitudes in the mountains. The White Poplar, by...

. Especially sensitive to temperature changes and moving northward almost immediately were Juniperus nana and J. communis, the dwarf and shrub Juniper
Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the...

 respectively, which reached a maximum density in the Pre-Boreal, before their niches were shaded out. Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...

 soon followed, for which reason the resulting open woodland is often called a birch or a pine-birch forest.
In the yet warmer early Boreal pollen zone V, Corylus avellana (hazel
The hazels are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.They have simple, rounded leaves with double-serrate margins...

) and pine expanded into the birch woodlands to such a degree that palynologists
Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...

 refer to the resulting ecology as the hazel-pine forest. In the late Boreal it was supplanted by the spread of a deciduous forest called the mixed-oak forest. Pine, birch and hazel were reduced in favor of Quercus, Ulmus, Tilia
Tilia is a genus of about 30 species of trees native throughout most of the temperate Northern Hemisphere. The greatest species diversity is found in Asia, and the genus also occurs in Europe and eastern North America, but not western North America...

and Alnus. The former tundra was now closed by a canopy of dense forest. In the marshland Typha latifolia
Typha latifolia
Typha latifolia is a perennial herbaceous plant in the genus Typha. It is found as a native plant species in North and South America, Europe, Eurasia, and Africa...

prevailed. Less cold-tolerant species such as ivy
Ivy, plural ivies is a genus of 12–15 species of evergreen climbing or ground-creeping woody plants in the family Araliaceae, native to western, central and southern Europe, Macaronesia, northwestern Africa and across central-southern Asia east to Japan and Taiwan.-Description:On level ground they...

 and mistletoe
Mistletoe is the common name for obligate hemi-parasitic plants in several families in the order Santalales. The plants in question grow attached to and within the branches of a tree or shrub.-Mistletoe in the genus Viscum:...

 were to be found in Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...



The new forest was populated with animals from refugia
In biology a refugium , sometimes termed simply a refuge, is a location of an isolated or relict population of a once more widespread species. This isolation can be due to climatic changes, geography, or human activities such as deforestation and over-hunting...

 in Italy, Spain and the Balkans. Animals such as Emys orbicularis (European pond tortoise), which require warmer temperatures, were to be found in Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

. The Eurasian golden plover
Eurasian Golden Plover
The European Golden Plover is a largish plover. This species is similar to two other golden plovers. American Golden Plover, Pluvialis dominiica, and Pacific Golden Plover, Pluvialis fulva, are both smaller, slimmer and relatively longer-legged than European Golden Plover, and both have grey...

 came as far north as Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...


Forest ungulates included: Cervidae Cervus elaphus (red deer
Red Deer
The red deer is one of the largest deer species. Depending on taxonomy, the red deer inhabits most of Europe, the Caucasus Mountains region, Asia Minor, parts of western Asia, and central Asia. It also inhabits the Atlas Mountains region between Morocco and Tunisia in northwestern Africa, being...

), Capreolus capreolus (roe deer
Roe Deer
The European Roe Deer , also known as the Western Roe Deer, chevreuil or just Roe Deer, is a Eurasian species of deer. It is relatively small, reddish and grey-brown, and well-adapted to cold environments. Roe Deer are widespread in Western Europe, from the Mediterranean to Scandinavia, and from...

), Alces alces (elk
The moose or Eurasian elk is the largest extant species in the deer family. Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a dendritic configuration...

), Sus scrofa
Wild boar, also wild pig, is a species of the pig genus Sus, part of the biological family Suidae. The species includes many subspecies. It is the wild ancestor of the domestic pig, an animal with which it freely hybridises...

(wild pig), and Bos primigenius (aurochs
The aurochs , the ancestor of domestic cattle, were a type of large wild cattle which inhabited Europe, Asia and North Africa, but is now extinct; it survived in Europe until 1627....

). Predators included: Canis lupus (wolf), Ursus arctos (brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

), Lynx lynx (lynx
A lynx is any of the four Lynx genus species of medium-sized wildcats. The name "lynx" originated in Middle English via Latin from Greek word "λύγξ", derived from the Indo-European root "*leuk-", meaning "light, brightness", in reference to the luminescence of its reflective eyes...

), Felis sylvestris
Wild cat
The wildcat is a small cat with several subspecies and a very broad distribution, found throughout most of Africa, Europe, and southwest and central Asia into India, China, and Mongolia. It is a hunter of small mammals, birds, and other creatures of a similar or smaller size. Sometimes included is...

(wildcat). Lepus europaeus (hare
Hares and jackrabbits are leporids belonging to the genus Lepus. Hares less than one year old are called leverets. Four species commonly known as types of hare are classified outside of Lepus: the hispid hare , and three species known as red rock hares .Hares are very fast-moving...


The inland waters would have contained mammal species such as Castor fiber (beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

), Lutra lutra (otter
The Otters are twelve species of semi-aquatic mammals which feed on fish and shellfish, and also other invertebrates, amphibians, birds and small mammals....

) and species of fish such as Esox lucius (northern pike
Northern Pike
The northern pike , is a species of carnivorous fish of the genus Esox...

) and Siluris glanis (catfish
Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...



The Preboreal-Boreal in Europe was a time of transition from the Palaeolithic cultures to the Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....

. Forests and drowned coastlands were places of plenty. Human settlements avoided the deep forest in favor of stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

s, lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

s, and especially bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...

s of the ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...


Pre-Boreal settlements have been found in north-central Europe, such as at Friesack
Friesack is a town in the Havelland district, in Brandenburg, Germany. It is situated northeast of Rathenow, and southwest of Neuruppin. It is known for its Mesolithic archaeological site.-Film shot in Friesack:...

. There an unusual find of net fragments made from plant fibers suggested that fishing was an important part of life.

Finds from another settlement at Vis, near the Vychegda River
Vychegda River
Vychegda is a river in the European part of Russia, tributary to the Northern Dvina. Its length is about . Its source is approximately west of the northern Ural Mountains. It flows roughly in western direction, through Komi Republic and Arkhangelsk Oblast. The largest city along the Vychegda is...

 in Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, offer more details of life in a settlement of the Boreal. Plant fibers were used for basket
A basket is a container which is traditionally constructed from stiff fibres, which can be made from a range of materials, including wood splints, runners, and cane. While most baskets are made from plant materials, other materials such as horsehair, baleen, or metal wire can be used. Baskets are...

s and for hafting bone points to shafts. Fishermen crossed the waters in bark boats plied by oar
An oar is an implement used for water-borne propulsion. Oars have a flat blade at one end. Oarsmen grasp the oar at the other end. The difference between oars and paddles are that paddles are held by the paddler, and are not connected with the vessel. Oars generally are connected to the vessel by...

s, and set nets. They also made hand-held nets from wooden hoops and plant fiber.

Food gathering continued in winter: ski
A ski is a long, flat device worn on the foot, usually attached through a boot, designed to help the wearer slide smoothly over snow. Originally intended as an aid to travel in snowy regions, they are now mainly used for recreational and sporting purposes...

s and sledge runners have been found. Reindeer
The reindeer , also known as the caribou in North America, is a deer from the Arctic and Subarctic, including both resident and migratory populations. While overall widespread and numerous, some of its subspecies are rare and one has already gone extinct.Reindeer vary considerably in color and size...

 continued to be hunted and probably herded. Bows, arrows, and spears have been found. Implements were likely to be embellished by sculpting in wood or bone. Only a few motifs were used: the elk's head, the snake, and human.

What is believed to be the oldest continuously inhabited city on Earth, the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

ern city of Jericho
Jericho ; is a city located near the Jordan River in the West Bank of the Palestinian territories. It is the capital of the Jericho Governorate and has a population of more than 20,000. Situated well below sea level on an east-west route north of the Dead Sea, Jericho is the lowest permanently...

, was first settled circa 11,000 BP, during the Preboreal period.

In Europe, the major culture was the Maglemosian (9000–6400 BC), extending into Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 and Russia. Localized cultures included the Nieman of Lithuania
Lithuania , officially the Republic of Lithuania is a country in Northern Europe, the biggest of the three Baltic states. It is situated along the southeastern shore of the Baltic Sea, whereby to the west lie Sweden and Denmark...

, the Kunda
History of Estonia
Estonia was settled near the end of the last glacial era, beginning from around 8500 BC. Before the German invasions in the 13th century proto-Estonians of the Ancient Estonia worshipped the spirits of nature...

 of Latvia
Latvia , officially the Republic of Latvia , is a country in the Baltic region of Northern Europe. It is bordered to the north by Estonia , to the south by Lithuania , to the east by the Russian Federation , to the southeast by Belarus and shares maritime borders to the west with Sweden...

 and Estonia
Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...

, the Azilian
The Azilian is a name given by archaeologists to an industry of the Epipaleolithic in northern Spain and southern France.It probably dates to the period of the Allerød Oscillation around 10,000 years ago and followed the Magdalenian culture...

 of France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, and the Epi-Gravettian of Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. Towards the end of the Mesolithic, local traditions began to multiply, perhaps due to influences from the south, or due to the general advance of culture.

In North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 the San Dieguito Complex and Lake Mojave Complex existed in this period, located in Southern California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

's coastal region and Mojave Desert
Mojave Desert
The Mojave Desert occupies a significant portion of southeastern California and smaller parts of central California, southern Nevada, southwestern Utah and northwestern Arizona, in the United States...

, and in northern Mexico's Sonoran Desert
Sonoran Desert
The Sonoran Desert is a North American desert which straddles part of the United States-Mexico border and covers large parts of the U.S. states of Arizona and California and the northwest Mexican states of Sonora, Baja California, and Baja California Sur. It is one of the largest and hottest...

 in the Yuma Desert
Yuma Desert
The Yuma Desert is a lower-elevation section of the Sonoran Desert in the southwestern United States and the northwest of Mexico. It is in the Salton basin. The desert contains areas of sparse vegetation and has notable areas of sand dunes. With an average rainfall less than 8 inches each...

 and Baja California peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...


External links

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