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The polar regions have undergone major changes in configuration of land masses and climate over millions of years. However, it is the geologically brief period beginning around 120,000 years before present (BP), including a warm interglacial followed by the Würm glaciation and then the interglacial in which we now live, which is most relevant. This chapter discusses changes during geological time: the ice ages; biological responses to long-term changes; and present-day global climate change and polar regions.

In 1872, Charles Abbott started finding artifacts in Delaware River gravels at Trenton, NJ, similar to European paleoliths. That discovery caught the eye of Harvard's Frederic Putnam, who provided financial aid, moral support and scientific respectability to the cause. Geologist George F. Wright seized the challenge of ascertaining the age of Abbott's finds. It was no easy task. Trenton was south of the limit of glacial advance by 60 miles, and had multiple gravel layers. Which were the same age as the glacier, and which were more recent? How did paleoliths fit that sequence, and the broader history of North American glaciation, then becoming more complicated with the realization there had been more than one glacial episode? The age of Abbott's paleoliths landed in a tug of war between competing camps. Nonetheless, he was certain the specimens were glacial in age, and in January of 1881 they took center stage at a Boston Society of Natural History meeting, where the city's scientific elite rose to bear witness to his discoveries. In scarcely a decade Abbott had shown that the future of American archaeology might be deep in its geological past.

This chapter focuses on the impacts of glacier melt on our oceans and related sea level rise. It discusses past and present sea levels and the relative influence of the ice age cycles. The chapter also reviews risks posed now to life on Earth due to glacier melt and related sea level rise, considering these in relation to ongoing and new flooding impacting coastal areas. It goes on to discuss the theories of Hot House Earth and Snowball Earth, the likelihood of these scenarios being realized, and the impact of high levels of CO₂ concentrations on the likelihood of either eventuality.

This chapter analyzes richness and rarity patterns of small mammals (rodents and marsupials) in Mediterranean and Temperate Chile. It tests for the effect of environmental factors that may explain richness and endemism variability after accounting for spatial autocorrelation. The chapter also analyzes the relationship between species traits and correlates of rarity (density and range size) after accounting for phylogenetic relatedness. It shows that energy input and to a lesser degree glaciations may explain richness patterns of small mammals from forest habitats in Chile, whereas glaciations and topographic heterogeneity are associated with endemicity patterns. The chapter observes that when phylogenetic relatedness was accounted for, the number of vegetarian types was the only ecological trait significantly associated with density and latitudinal range. It notes that the results reinforce the importance of energy availability and productivity in determining patterns in biodiversity.

Many events in global tectonics and high latitude climate had significant effects on Cenozoic climate evolution. This chapter explores three revolutions in climate research that have dramatically altered our perception of global and African climate. First, the discovery that large magnitude climate events occurred abruptly, sometimes in as little as decades, has prompted high-resolution paleoclimate reconstructions and new conceptions of climate dynamics. Second, recent climate studies have revealed significant tropical climate variability. Modern observational climate data have indicated that the largest mode of global interannual climate variability is the El Niño Southern Oscillation in the tropical Pacific. Revised estimates of tropical sea surface temperatures during global cool and warm events have revealed significant tropical sensitivity to global climate change. Third, the role of the tropics in global climate change has been reconceptualized. This chapter also discusses the modern climate of Africa, abrupt events in the Paleocene, Oligocene Antarctic glaciation and Southern African climate, mid-Miocene climate change in Africa, plio-Pleistocene environmental change, cool and dry conditions during the Last Glacial Maximum, and Holocene climate.

From continental macroclimate to microalluvial salt crusts, geology is a dominant factor that influences patterns and processes in the Alaskan boreal forest. In this chapter, we outline important geologic processes as a foundation for subsequent chapters that discuss the soil, hydrology, climate, and biota of the Alaskan boreal forest. We conclude the chapter with a discussion of interior Alaska from a regional perspective. Alaska can be divided into four major physiographic regions. The arctic coastal plain is part of the Interior Plains physiographic division of North America, analogous to the great plains east of the Rocky Mountains. The arctic coastal plain is predominantly alluvium underlaid by hundreds of meters of permafrost, resulting in many thaw lakes and ice wedges. South of the arctic coastal plain lies the Northern Cordillera, an extension of the Rocky Mountain system dominated by the Arctic Foothills, Brooks Range, Baird Mountains, and Delong Mountains. These mountains were glaciated during the Pleistocene. South of the Brooks Range lies interior Alaska, which is an intermontane plateau region analogous to the Great Basin/Colorado Plateau regions. This extensive region is characterized by wide alluvium-covered lowlands such as the Yukon Flats, Tanana Valley, and Yukon Delta, as well as moderate upland hills, domes, and mountains. Largely unglaciated, this region served as a refugium for biota during glacial periods. With the Northern and Southern Cordilleras acting as barriers, the major rivers of this region have long, meandering paths to the Bering Sea. The Southern Cordillera is composed of two mountain ranges: the Alaska Range to the north and the Kenai/Chugach/Wrangell-St. Elias Mountains to the south. The lowland belt between these mountains includes the Susitna and Copper River lowlands. The entire Southern Cordillera was glaciated during the Pleistocene and today has extensive mountain glaciers. Much of Alaska is made up of multiple geologic fragments that have been rafted together by the movements of the major plates called tectonic terranes (Thorson 1986, Connor and O’Haire 1988). Plate-tectonic theory explains such observations as the changing distribution of fossils with geologic time, the deep Aleutian Trench, high Alaskan mountain barriers, and mountain glaciers.

This chapter shows how planetary cooling has culminated in a series of periodic glaciations of the Northern hemisphere – the recent ‘ice ages’ – which have become progressively longer and deeper. Although they are paced by variations in the Earth's orbit, they are increasingly dominated by internal oscillations and amplifying feedbacks. The ice ages illustrate the tightly coupled behaviour of the Earth system, indicating that the climate system which we have evolved in is unusually sensitive. At these time scales, oscillations of climate that are paced by the orbital wobbles of the Earth, known as the Milankovitch cycles, become very apparent. The wobbles occur because the Earth's orbit around the sun does not repeat exactly each year but is subject to variations, due ultimately to the presence of other bodies in the solar system.

This chapter studies the character of the coupled changes in the phosphorus and carbon cycles during the last 160 million years and proposes feedback mechanisms between the two cycles. The effects of the proposed feedback systems on the biosphere are explored, especially their capacity to regulate environmental conditions in a Gaian sense. For this purpose, this chapter uses marine phosphorus and carbon burial rates, a modeled atmospheric CO₂ curve, and stable carbon isotopes as proxies for temporal change in the global phosphorus and carbon cycles. Based on the temporal changes within these proxies, the chapter postulates a period of fundamental change in feedback between weathering, productivity, and climate at around 32 million years ago, which is explained by the onset of major glaciation. This suggests that feedback mechanisms may not be uniform throughout Earth’s history but may change during environmental change.

Present-day environments cannot be completely understood without knowledge of their history since the last ice age. Paleoecological studies show that the modern ecosystems did not spring full-blown onto the Rocky Mountain region within the last few centuries. Rather, they are the product of a massive reshuffling of species that was brought about by the last ice age and indeed continues to this day. Chronologically, this chapter covers the late Quaternary Period: the last 25,000 years. During this interval, ice sheets advanced southward, covering Canada and much of the northern tier of states in the United States. Glaciers crept down from mountaintops to fill high valleys in the Rockies and Sierras. The late Quaternary interval is important because it bridges the gap between the ice-age world and modern environments and biota. It was a time of great change, in both physical environments and biological communities. The Wisconsin Glaciation is called the Pinedale Glaciation in the Rocky Mountain region (after terminal moraines near the town of Pinedale, Wyoming; see chapter 4). The Pinedale Glaciation began after the last (Sangamon) Interglaciation, perhaps 110,000 radiocarbon years before present (yr BP), and included at least two major ice advances and retreats. These glacial events took different forms in different regions. The Laurentide Ice Sheet covered much of northeastern and north-central North America, and the Cordilleran Ice Sheet covered much of northwestern North America. The two ice sheets covered more than 16 million km2 and contained one third of all the ice in the world’s glaciers during this period. The history of glaciation is not as well resolved for the Colorado Front Range region as it is for regions farther north. For instance, although a chronology of three separate ice advances has been established for the Teton Range during Pinedale times, in northern Colorado we know only that there were earlier and later Pinedale ice advances. We do not know when the earlier advance (or multiple advances) took place. However, based on geologic evidence (Madole and Shroba 1979), the early Pinedale glaciation was more extensive than the late Pinedale was.

The Lipalian or Vendian Period, which occurred 600–541 million years ago, begins and ends with global environmental perturbations. It begins as the worst glaciation on record draws to a close. It ends with a sudden appearance of abundant skeletonized animals that mark the beginning of Cambrian ecology. Several key events in Earth history occur during the Lipalian, bracketed between severe glaciation and the initiation of modern marine ecosystems. The most notable of these events is the appearance of an unusual and conspicuous marine biota, the “Garden of Ediacara.” This biota appears to have characteristics inherited from its sojourn beneath the ice. This chapter examines the role the cryophilic biota, consisting largely of cyanobacteria and chryosphyte and chlorophyte algae, may have played in ending the great ice age. It is hypothesized here that these microbes induced albedo reductions and other changes that rapidly improved global climate.

This chapter describes the earliest archaeological findings of human groups—the Pleistocene fossils—from the Ryukyu Islands. These fossils range in date from 32,000 to 16,000 years ago. From 23,000 to 18,000 BP, at the height of the Wurm Glaciation, sea level was lower by about 140 m; consequently, a large land mass was available for habitation by people whose remains were found in Minatogawa and other sites. Late Pleistocene Homo sapiens had to cross water to reach the few large islands of the Ryukyus in the Late Pleistocene. Between the Late Pleistocene discoveries and subsequent Holocene archaeological sites there is a gap of about 8,000 to 9,000 years.

The Mediterranean region has had a long and complex history. The phasing of three main historical elements forms a Mediterranean triptych: geology, climate, and human activities. The geological fragmentation of the Mediterranean into distinct microregions and tectonic movement of its different microplates has continually reshaped the configuration of the terrestrial landscapes, islands, and mountains. Many areas have been land bridge connections across the sea. The Mediterranean region has a characteristic climate, the essential element of which is the occurrence of a summer drought. Although initial trends towards aridity are ancient, the Mediterranean climate only dates to the Pliocene. Climatic oscillations since its onset have caused sea level changes, influencing the appearance and disappearance of land bridge connections across different parts of the Mediterranean Sea, causing species’ range sizes to expand and contract in repeated phases. Finally, nowhere else in Europe has had such a long history of human presence and activity. In the last three millennia, the impact of human activities on the landscape has been dramatic in terms of the evolution of the mosaic landscape we now observe. The phased history of these three factors is at the heart of plant evolution in the Mediterranean.

Gifford Pinchot first met John Muir in 1896, while on a trip through the West to study possible sites for new forest preserves. Pinchot was much impressed by Muir, twenty-seven years his senior, and recalled the meeting fifty years later in his autobiography. He described Muir as “cordial, and a most fascinating talker, I took to him at once.” Muir, in his writings of this period, was explicitly complimentary of Pinchot’s efforts at sustainable forestry. At the Grand Canyon, Muir and Pinchot struck off on their own and “spent an unforgettable day on the rim of the prodigious chasm, letting it soak in.” They came across a tarantula and Muir wouldn’t let Pinchot kill it: “He said it had as much right there as we did.” Within a year, however, Muir had complained bitterly and publicly about Pinchot’s decision to allow grazing in the national forest reserves. This rift between the Moralist (Muir) and the Aggregator (Pinchot) shaped the two wings of the environmental movement, and its original configuration owes much to attitudes developed in the early life and work of each man. Muir entered the University of Wisconsin in 1861, the year the Civil War broke out. Although he was almost twenty-three, his last formal schooling had been interrupted at the age of eleven, when his family emigrated from Scotland. His father, Daniel, a religious zealot, had no use for any book but the Bible. The elder Muir, who joined ever more extreme sects in search of one sufficiently pure and exacting, chose eighty acres of virgin land and put his eldest son John to work clearing it. Days were spent cutting trees and grubbing out roots, and nights were given over to memorizing Scripture. Daniel Muir planted only corn and wheat for cash crops, and the farmland was worn out in only eight years. Choosing a new and larger plot, the family moved and repeated the process. Again, the hardest work fell to John as his father spent all of his time studying the Bible and preaching to anyone who would listen.

In just a few years, the magnetic bar-code secreted beneath the world’s oceans had provided detailed intelligence on the motions of the plates. When combined with other data from the sea floor, this allowed geophysicists to reconstruct the history of entire ocean basins following the rifting of Pangea. Some folk, however, are never happy, and ‘glass-half-empty’ types might well have complained that, impressive as all this was, it accounted for less than 200 million of the 4500 million years of Earth history, i.e. just 4%. What about that other 96%? Did plate tectonics operate through part or all of this long history and, in any case, how could you ever know, since the evidence had all been shredded by the closure of earlier oceans? There was hope: the same process that had so conveniently sequestered the recent history of the plates in the sea floor had also been at work throughout much of earlier geological time, recording the story in rocks onshore. By comparison with the high-definition picture of plate motions offered by bar-codes and fracture zones, this recording was monochrome, fuzzy, and incomplete. Yet, by the mid-1950s, it had already provided conclusive evidence that continents were truly mobile. Curiously, hardly anyone noticed.

Our attempts to reconstruct the climate of the distant Archaean in Chapter 1 might seem a little like reading a volume of Tolstoy’s War and Peace recovered from a burnt-out house. Most of the pages have turned to ash, and only some scattered sentences remain on a few charred pages. The Proterozoic Eon that followed began 2.5 billion years ago, thus is not quite so distant from us in time. We know it a little better than the Archaean—at least a handful of pages from its own book have survived. And this book is long—the Proterozoic lasted nearly two billion years. This is as long as the Hadean and Archaean together, and not far short of half of Earth’s history. Like many a soldier’s account of war, it combined long periods of boredom and brief intervals of terror—or their climatic equivalents, at least. The latter included the most intense glaciations that ever spread across the Earth. Some of these may have converted the planet into one giant snowball. The earliest traces of glaciation on Earth are seen even before the Proterozoic, in rock strata of Archaean age, 2.9 billion years old, near the small South African town of Pongola. These rocks include sedimentary deposits called tillites, which are essentially a jumble of rock fragments embedded in finer sediment. The vivid, old-fashioned term for such deposits is ‘boulder clays’, while the newer and more formal name is ‘till’ for a recent deposit and ‘tillite’ for the hardened, ancient version. Many of the ancient blocks and boulders in the tillites of Pongola are grooved and scratched—a tell-tale sign that they have been dragged along the ground by debris-rich ice. This kind of evidence is among the first ever employed by scientists of the mid-nineteenth century, such as Louis Agassiz and William Buckland, to tell apart ice-transported sediments from superficially similar ones that had formed as boulder-rich slurries when rivers flooded or volcanoes erupted. Ice, then, appeared on Earth in Archaean times.

Several physical features combine to make Southeast Asia one of the most distinct and unique coastal regions in the world. The mainland or continental part of Southeast Asia consists of a number of peninsulas extending south and southeast from the Asian continent and separated by gulfs and bays. The world’s two largest archipelagos form the islands of Southeast Asia. During much of the Pleistocene, a large part of the South China Sea was dry land, and the islands of Sumatra, Java, and Borneo were linked to the mainland by the exposed shallow Sunda Shelf. Southeast Asia comes under the influence of the monsoons, or seasonal winds, which have an important impact on its coasts. The region is also a high biodiversity zone, characterized by its rich coral reefs and mangroves. This chapter examines the coastal environments of Southeast Asia in three stages. First, the major elements that make the coastal environments of Southeast Asia distinctive are discussed. The focus is on the coastal processes, as the geological framework and Quaternary have been covered in earlier chapters. Secondly, the various coastal environments in the region (excluding estuaries and deltas discussed in Chapter 13) are described next in terms of their extent, characteristics, and significance, with sufficient examples given to show their variability. Finally, the chapter ends with an assessment of the major environmental problems facing the region’s coastal environments—coastal erosion and rising sea level associated with climate change. Overall, this chapter provides the physical basis for a better appreciation of coastal development in Southeast Asia. The coastal environments of Southeast Asia bear the impact of significant geological and climatic factors. Geologically, the core of the region is an extension of the Eurasian Plate meeting the Indo-Australian and the Pacific Plates and two lesser ones (Philippines and Molucca Sea) with mountain chains trending in a general north–south direction. The island of New Guinea is part of the Indo-Australia Plate. Island arcs have developed along the convergent margins, and many are volcanically active and also associated with shallow to deep earthquakes.

Deltas and estuaries are actively evolving suites of landforms formed where rivers meet the sea. Deltas are characteristically subaerial (and subaqueous) sediment wedges that protrude from the shoreline, whereas estuaries are typically tidally influenced lower parts of rivers in which the shoreline recedes inland. However, the individual distributaries of deltas, which may themselves be cuspate, exhibit estuarine characteristics, and it is convenient to use the term ‘deltaic–estuarine’ to describe river mouth tidal and alluvial plains. There are extensive low-lying coastal and deltaic–estuarine plains throughout Southeast Asia. These represent productive and relatively easily settled land, which has led to clearance of the natural vegetation of many of these plains for agriculture, silviculture, or settlement. Deltaic–estuarine plains are geologically young, responding to Late Quaternary sea-level and climatic fluctuations, and actively undergoing change in the modern landscape. Most have adopted their present form only in the past few thousand years, and are still active centres of deposition. Worldwide expansion of deltas occurred in the early to mid-Holocene as a result of deceleration of postglacial sea-level rise and the coincidence of sea level with extensive low-gradient shorelines (Stanley and Warne 1994). The formation of deltaic–estuarine plains in semi-arid areas may have been a catalyst for the appearance of civilizations based upon cultivation (Stanley and Warne 1993). Deltas in Southeast Asia, however, presented major challenges to pre-technical societies, as a result of their propensity to flood, poor access across the many bifurcating channels, and malaria, and were slower to be colonized (Büdel 1966). However, they have subsequently become important areas supporting large populations, particularly as a result of successful management of inundation for the cultivation of rice (van de Goor 1966). Overbank flooding is a prominent feature of most deltas and assures nutrient re-enrichment of fertile, but immature, soils supporting intensive farming. On the other hand, such flooding can also represent a major hazard, damaging property and in some cases resulting in loss of life. It is often controlled, or control over the extent of flooding is sought through engineering works.

Inselbergs, tors, boulder fields, and pediments are repetitive landforms of many low- to mid-latitude granite landscapes, whether in humid or in arid environments. Although there have been attempts to link these landforms to certain specific climatic environments, their actual distribution, as shown in the preceding chapters, speaks clearly for minor climatic control in their development. Therefore, identification of a ‘typical’ granite rainforest, or savanna, or desert landscape does not seem possible. Each of these environments is known to host a variety of distinctive landscapes supported by granite, which will be explored in the next chapter. Likewise, cold environments in high latitudes have long been considered as having a very distinctive geomorphology, in which the factor of rock control matters little, but repeated freezing and thawing is critical. This view is difficult to maintain any longer, especially in the light of recent progress in periglacial geomorphology. The effects of glaciation are more evident, but even there the role of bedrock must not be neglected and formerly glaciated granite terrains do show certain specific features. Many granite terrains are located in cold environments, or have experienced cold-climate conditions in the relatively recent past of the Pleistocene. Therefore, it is reasonable to expect that their geomorphic evolution has been influenced by a suite of surface processes characteristic of such settings, collectively termed as ‘periglacial’. Present-day periglacial conditions typify such granite areas as the uplands of Alaska, Yukon, and the northern Rocky Mountains, much of the Canadian Shield, coastal strips of Greenland, northern Scandinavia, extensive tracts of Siberia, and the Tibetan Plateau. Granite areas located further south, in the British Isles, the Iberian Peninsula, the Massif Central, the Harz Mountains, and the Bohemian Massif, were affected by periglacial conditions for most of the Pleistocene. In fact, the most elevated parts of these mountains and uplands experience a mild periglacial environment even today and winter temperatures may remain below 0°C for weeks. The efficacy of present-day frost action is however limited by the insulating snow cover. Some of the granite areas of the southern hemisphere are, or were, within the periglacial realm too.

Climate change is among the most talked about and investigated global risks. No other environmental issue receives quite as much attention in the popular press, even though the impacts of pandemics and asteroid strikes, for instance, may be much more severe. Since the first Intergovernmental Panel on Climate Change (IPCC) report in 1990, significant progress has been made in terms of (1) establishing the reality of anthropogenic climate change and (2) understanding enough about the scale of the problem to establish that it warrants a public policy response. However, considerable scientific uncertainty remains. In particular scientists have been unable to narrow the range of the uncertainty in the global mean temperature response to a doubling of carbon dioxide from pre-industrial levels, although we do have a better understanding of why this is the case. Advances in science have, in some ways, made us more uncertain, or at least aware of the uncertainties generated by previously unexamined processes. To a considerable extent these new processes, as well as familiar processes that will be stressed in new ways by the speed of twentyfirst century climate change, underpin recent heightened concerns about the possibility of catastrophic climate change. Discussion of ‘tipping points’ in the Earth system (for instance Kemp, 2005; Lenton, 2007) has raised awareness of the possibility that climate change might be considerably worse than we have previously thought, and that some of the worst impacts might be triggered well before they come to pass, essentially suggesting the alarming image of the current generation having lit the very long, slow-burning fuse on a climate bomb that will cause great devastation to future generations. Possible mechanisms through which such catastrophes could play out have been developed by scientists in the last 15 years, as a natural output of increased scientific interest in Earth system science and, in particular, further investigation of the deep history of climate. Although scientific discussion of such possibilities has usually been characteristically guarded and responsible, the same probably cannot be said for the public debate around such notions.

Modern physics suggests several exotic ways in which things could go terribly wrong on a very large scale. Most, but not all, are highly speculative, unlikely, or remote. Rare catastrophes might well have decisive influences on the evolution of life in the universe. So also might slow but inexorable changes in the cosmic environment in the future. Only a twisted mind will find joy in contemplating exotic ways to shower doom on the world as we know it. Putting aside that hedonistic motivation, there are several good reasons for physicists to investigate doomsday scenarios that include the following: Looking before leaping: Experimental physics often aims to produce extreme conditions that do not occur naturally on Earth (or perhaps elsewhere in the universe). Modern high-energy accelerators are one example; nuclear weapons labs are another. With new conditions come new possibilities, including – perhaps – the possibility of large-scale catstrophe. Also, new technologies enabled by advances in physics and kindred engineering disciplines might trigger social or ecological instabilities. The wisdom of ‘Look before you leap’ is one important motivation for considering worst-case scenarios. Preparing to prepare: Other drastic changes and challenges must be anticipated, even if we forego daring leaps. Such changes and challenges include exhaustion of energy supplies, possible asteroid or cometary impacts, orbital evolution and precessional instability of Earth, evolution of the Sun, and – in the very long run – some form of ‘heat death of the universe’. Many of these are long-term problems, but tough ones that, if neglected, will only loom larger. So we should prepare, or at least prepare to prepare, well in advance of crises. Wondering: Catastrophes might leave a mark on cosmic evolution, in both the physical and (exo)biological senses. Certainly, recent work has established a major role for catastrophes in sculpting terrestrial evolution (see http://www.answers.com/topic/timeline-of-evolution). So to understand the universe, we must take into account their possible occurrence. In particular, serious consideration of Fermi’s question ‘Where are they?’, or logical pursuit of anthropic reasoning, cannot be separated from thinking about how things could go drastically wrong. This will be a very unbalanced essay.