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The late Miocene Adu-Asa Formation comprises major sedimentary and volcanic units that crop out along the densely faulted and tilted frontal blocks of the western rift margin of the transition zone between the northern Main Ethiopian Rift (MER) and the southern Afar Rift. This chapter discusses the geological and tectonic processes that led to the origin and evolution of the rift basin of the transition zone. It highlights a decade-long geological and paleontological reconnaissance and focuses investigation along the strike of the frontal fault blocks of the western rift margin of the Middle Awash study area.

Recent discoveries of hominid remains older than 5 Ma have afforded new perspectives on the origin of the hominid clade. This chapter describes and assesses the key evidence bearing on these issues—the remains of Ardipithecus kadabba from the Middle Awash study area of the Afar Rift. It introduces the major morphological features of the known Ardipithecus kadabba specimens and also infers possible ancestral ape conditions from the morphologies shared by extant great apes and the collective late and middle Miocene fossil ape record.

This chapter considers the paleoenvironment of the Middle Awash study area in the Afar Rift of Ethiopia. Different aspects of the large mammalian faunal communities from the Asa Koma and Kuseralee Members are examined. The chapter examines the community structure based on locomotor and dietary variables, relative abundances of indicator taxa, and ecomorphology. Independent verification of the results based on large mammalian fauna have been derived from fish, bird, and small mammal faunas and from geological and stable isotopic data.

This is the first substantive career interview with installation artist Janet Biggs. Biggs discusses her motivation for making installations, rather than theatrical films, and the different ways in which moviegoers and visitors to installations experience moving image art. Biggs describes her experiences traveling to the ends of the earth to record compelling imagery in the Arctic, at a sulfur-mining operation inside a volcano in Indonesia, and in the Afar triangle region of Ethiopia, Eritrea, and Djibouti, Her many wide-ranging conceptual videos explore various forms of physical labor and athletic endeavor from football to water ballet and synchronized swimming to NASCAR, as well as the mysteries of Alzheimer’s disease and attempts to break the on-land speed record.

Anyone who drives through southern Idaho on Interstates 84 or 15 must endure hours and hundreds of miles of monotonous scenery: the vast, flat landscape of the Snake River Plain. In many areas, sagebrush and solidified basalt lava flows extend toward distant mountain ranges, while in other places, farmers have cultivated large expanses of volcanic soil to grow Idaho’s famous potatoes. Southern Idaho’s topography was not always so dull. Mountain ranges once ran through the region. Thanks to the Yellowstone hotspot, however, the pre-existing scenery was destroyed by several dozen of the largest kind of volcanic eruption on Earth—eruptions that formed gigantic craters, known as calderas, measuring a few tens of miles wide. Some 16.5 million years ago, the hotspot was beneath the area where Oregon, Nevada, and Idaho meet. It produced its first big caldera-forming eruptions there. As the North American plate of Earth’s surface drifted southwest over the hotspot, about 100 giant eruptions punched through the drifting plate, forming a chain of giant calderas stretching almost coo miles from the Oregon—Nevada—Idaho border, northeast across Idaho to Yellowstone National Park in northwest Wyoming. Yellowstone has been perched atop the hotspot for the past 2 million years, and a 45-by-30-mile-wide caldera now forms the heart of the national park. After the ancient landscape of southern and eastern Idaho was obliterated by the eruptions, the swath of calderas in the hotspot’s wake formed the eastern two-thirds of the vast, 50-mile-wide valley now known as the Snake River Plain. The calderas eventually were buried by basalt lava flows and sediments from the Snake River and its tributaries, concealing the incredibly violent volcanic history of the Yellowstone hotspot. Yet we now know that the hotspot created much of the flat expanse of the Snake River Plain. Like a boat speeding through water and creating an arc-shaped wave in its wake, the hotspot also left in its wake a parabola-shaped pattern of high mountains and earthquake activity flanking both sides of the Snake River Plain.