The Holocene is a geologic epoch that follows directly after the Pleistocene. Continental motions due to
plate tectonics are less than a kilometre over a span of only 10,000 years. However, ice melt caused world
sea levels to rise about in the early part of the Holocene and another 30 m in the later part of the Holocene. In addition, many areas above about
40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as due to
post-glacial rebound over the late Pleistocene and Holocene, and are still rising today. The sea-level rise and temporary
land depression allowed temporary marine incursions into areas that are now far from the sea. For example, marine fossils from the Holocene epoch have been found in locations such as
Vermont and
Michigan. Other than higher-latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed,
floodplain, and
cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely
tectonic uplift of non-glacial origin. Post-glacial rebound in the
Scandinavia region resulted in a shrinking
Baltic Sea. The region continues to rise, still causing weak
earthquakes across Northern Europe. An equivalent event in North America was the rebound of
Hudson Bay, as it shrank from its larger, immediate post-glacial
Tyrrell Sea phase, to its present boundaries. ==Climate== (bottom) and Holocene (top) The climate throughout the Holocene has shown significant variability despite ice core records from Greenland suggesting a more stable climate following the preceding ice age. Marine chemical fluxes during the Holocene were lower than during the Younger Dryas, but were still considerable enough to imply notable changes in the climate. The temporal and spatial extent of climate change during the Holocene is an area of considerable uncertainty, with
radiative forcing recently proposed to be the origin of cycles identified in the North Atlantic region. Climate cyclicity through the Holocene (
Bond events) has been observed in or near marine settings and is strongly controlled by glacial input to the North Atlantic. Periodicities of ≈2500, ≈1500, and ≈1000 years are generally observed in the North Atlantic. At the same time spectral analyses of the continental record, which is remote from oceanic influence, reveal persistent periodicities of 1,000 and 500 years that may correspond to solar activity variations during the Holocene Epoch. A 1,500-year cycle corresponding to the North Atlantic oceanic circulation may have had widespread global distribution in the Late Holocene. The Greenland ice core records indicate that climate changes became more regional and had a larger effect on the mid-to-low latitudes and mid-to-high latitudes after ~5600 B.P. Human activity through land use changes already by the Mesolithic had major ecological impacts; it was an important influence on Holocene climatic changes, and is believed to be why the Holocene is an atypical interglacial that has not experienced significant cooling over its course. From the start of the
Industrial Revolution onwards, large-scale anthropogenic greenhouse gas emissions caused the Earth to warm. Likewise, climatic changes have induced substantial changes in human civilisation over the course of the Holocene. During the transition from the last glacial to the Holocene, the
Huelmo–Mascardi Cold Reversal in the
Southern Hemisphere began before the Younger Dryas, and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. It appears that this was influenced by the residual glacial ice remaining in the
Northern Hemisphere until the later date. The first major phase of Holocene climate was the
Preboreal. At the start of the Preboreal occurred the
Preboreal Oscillation (PBO). The
Holocene Climatic Optimum (HCO) was a period of warming throughout the globe but was not globally synchronous and uniform. Following the HCO, the global climate entered a broad trend of very gradual cooling known as
Neoglaciation, which lasted from the end of the HCO to before the
Industrial Revolution. The LIA was the coldest interval of time of the past two millennia. Following the Industrial Revolution, warm decadal intervals became more common relative to before as a consequence of anthropogenic greenhouse gases, resulting in progressive global warming. though solar activity has continued to play a role.
Europe (right)
Drangajökull, Iceland's northernmost glacier, melted shortly after 9,200 BP. In
Northern Germany, the Middle Holocene saw a drastic increase in the amount of raised bogs, most likely related to sea level rise. Although human activity affected geomorphology and landscape evolution in Northern Germany throughout the Holocene, it only became a dominant influence in the last four centuries. In the
French Alps, geochemistry and lithium isotope signatures in lake sediments have suggested gradual soil formation from the
Last Glacial Period to the
Holocene climatic optimum, and this soil development was altered by the settlement of human societies. Early anthropogenic activities such as deforestation and agriculture reinforced soil erosion, which peaked in the
Middle Ages at an unprecedented level, marking human forcing as the most powerful factor affecting surface processes. The sedimentary record from
Aitoliko Lagoon indicates that wet winters locally predominated from 210 to 160 BP, followed by dry winter dominance from 160 to 20 BP.
Africa North Africa, dominated by the
Sahara Desert in the present, was instead a savanna dotted with large lakes during the Early and Middle Holocene, regionally known as the
African Humid Period (AHP). The northward migration of the
Intertropical Convergence Zone (ITCZ) produced increased monsoon rainfall over North Africa. The lush vegetation of the Sahara brought an increase in
pastoralism. The AHP ended around 5,500 BP, after which the Sahara began to dry and become the desert it is today. A stronger East African Monsoon during the Middle Holocene increased precipitation in East Africa and raised lake levels. Around 800 AD, or 1,150 BP, a marine transgression occurred in southeastern Africa; in the Lake Lungué basin, this sea level highstand occurred from 740 to 910 AD, or from 1,210 to 1,040 BP, as evidenced by the lake's connection to the Indian Ocean at this time. This transgression was followed by a period of transition that lasted until 590 BP, when the region experienced significant aridification and began to be extensively used by humans for livestock herding. In the
Kalahari Desert, Holocene climate was overall very stable and environmental change was of low amplitude. Relatively cool conditions have prevailed since 4,000 BP.
Middle East , a commonly cited example of a
proto-city, 7300 BC In the
Middle East, the Holocene brought a warmer and wetter climate, in contrast to the preceding cold, dry
Younger Dryas. The Early Holocene saw the advent and spread of agriculture in the
Fertile Crescent—
sheep,
goat,
cattle, and later
pig were domesticated, as well as cereals, like
wheat and
barley, and
legumes—which would later
disperse into much of the world. This '
Neolithic Revolution', likely influenced by Holocene climatic changes, included an increase in
sedentism and population, eventually resulting in the world's first large-scale state societies in
Mesopotamia and
Egypt. During the Middle Holocene, the
Intertropical Convergence Zone, which governs the incursion of monsoon precipitation through the
Arabian Peninsula, shifted southwards, resulting in increased aridity. In the Middle to Late Holocene, the coastline of the
Levant and
Persian Gulf receded, prompting a shift in human settlement patterns following this marine regression.
Central Asia Central Asia experienced glacial-like temperatures until about 8,000 BP, when the Laurentide Ice Sheet collapsed. In
Xinjiang, long-term Holocene warming increased meltwater supply during summers, creating large lakes and oases at low altitudes and inducing enhanced moisture recycling. In the
Tien Shan, sedimentological evidence from Swan Lake suggests the period between 8,500 and 6,900 BP was relatively warm, with steppe meadow vegetation being predominant. An increase in
Cyperaceae from 6,900 to 2,600 BP indicates cooling and humidification of the Tian Shan climate that was interrupted by a warm period between 5,500 and 4,500 BP. After 2,600 BP, an alpine steppe climate prevailed across the region. Sand dune evolution in the Bayanbulak Basin shows that the region was very dry from the Holocene's beginning until around 6,500 BP, when a wet interval began. In the
Tibetan Plateau, the moisture optimum spanned from around 7,500 to 5,500 BP. The
Tarim Basin records the onset of significant aridification around 3,000-2,000 BP.
South Asia After 11,800 BP, and especially between 10,800 and 9,200 BP,
Ladakh experienced tremendous moisture increase most likely related to the strengthening of the Indian Summer Monsoon (ISM). From 9,200 to 6,900 BP, relative aridity persisted in Ladakh. A second major humid phase occurred in Ladakh from 6,900 to 4,800 BP, after which the region was again arid. From 900 to 1,200 AD, during the MWP, the ISM was again strong as evidenced by low δ18O values from the Ganga Plain. The sediments of
Lonar Lake in
Maharashtra record dry conditions around 11,400 BP that transitioned into a much wetter climate from 11,400 to 11,100 BP due to intensification of the ISM. Over the Early Holocene, the region was very wet, but during the Middle Holocene from 6,200 to 3,900 BP, aridification occurred, with the subsequent Late Holocene being relatively arid as a whole. Coastal southwestern India experienced a stronger ISM from 9,690 to 7,560 BP, during the HCO. From 3,510 to 2,550 BP, during the Late Holocene, the ISM became weaker, although this weakening was interrupted by an interval of unusually high ISM strength from 3,400 to 3,200 BP.
East Asia Southwestern China experienced long-term warming during the Early Holocene up until ~7,000 BP. Northern China experienced an abrupt aridification event approximately 4,000 BP. From around 3,500 to 3,000 BP, northeastern China underwent a prolonged cooling, manifesting itself with the disruption of Bronze Age civilisations in the region. Eastern and southern China, the monsoonal regions of China, were wetter than present in the Early and Middle Holocene. Lake Huguangyan's TOC, δ13Cwax, δ13Corg, δ15N values suggest the period of peak moisture lasted from 9,200 to 1,800 BP and was attributable to a strong East Asian Summer Monsoon (EASM). Late Holocene cooling events in the region were dominantly influenced by solar forcing, with many individual cold snaps linked to solar minima such as the Oort,
Wolf,
Spörer, and
Maunder Minima. A notable cooling event in southeastern China occurred 3,200 BP. Strengthening of the winter monsoon occurred around 5,500, 4,000, and 2,500 BP. Monsoonal regions of China became more arid in the Late Holocene.
Southeast Asia Before 7,500 BP, the
Gulf of Thailand was exposed above sea level and was very arid. A marine transgression occurred from 7,500 to 6,200 BP amidst global warming.
North America During the Middle Holocene, western North America was drier than present, with wetter winters and drier summers. After the end of the thermal maximum of the HCO around 4,500 BP, the
East Greenland Current underwent strengthening. A massive megadrought occurred from 2,800 to 1,850 BP in the
Great Basin. Eastern North America underwent abrupt warming and humidification around 10,500 BP and then declined from 9,300 to 9,100 BP. The region has undergone a long term wettening since 5,500 BP occasionally interrupted by intervals of high aridity. A major cool event lasting from 5,500 to 4,700 BP was coeval with a major humidification before being terminated by a major drought and warming at the end of that interval.
South America During the Early Holocene, relative sea level rose in the
Bahia region, causing a landward expansion of mangroves. During the Late Holocene, the mangroves declined as sea level dropped and freshwater supply increased. In the
Santa Catarina region, the maximum sea level highstand was around 2.1 metres above present and occurred about 5,800 to 5,000 BP. Sea levels at
Rocas Atoll were likewise higher than present for much of the Late Holocene.
Australia The Northwest Australian Summer Monsoon was in a strong phase from 8,500 to 6,400 BP, from 5,000 to 4,000 BP (possibly until 3,000 BP), and from 1,300 to 900 BP, with weak phases in between and the current weak phase beginning around 900 BP after the end of the last strong phase.
New Zealand Ice core measurements imply that the
sea surface temperature (SST) gradient east of New Zealand, across the subtropical front (STF), was around 2 degrees Celsius during the HCO. This temperature gradient is significantly less than modern times, which is around 6 degrees Celsius. A study utilizing five SST proxies from 37°S to 60°S latitude confirmed that the strong temperature gradient was confined to the area immediately south of the STF, and is correlated with reduced westerly winds near New Zealand. Since 7,100 BP, New Zealand experienced 53 cyclones similar in magnitude to
Cyclone Bola.
Pacific Evidence from the
Galápagos Islands shows that the
El Niño–Southern Oscillation (ENSO) was significantly weaker during the Middle Holocene, but that the strength of ENSO became moderate to high over the Late Holocene. ==Ecological developments==