The Holocene and Global Climate Change

The Pleistocene Epoch, often referred to as the Ice Age, lasted from approximately 2.6 million to 11,700 years ago. The last major ice advance began about 110,000 years ago, and the most recent episode of maximum ice coverage, the Last Glacial Maximum, began about 26,500 years ago and ended approximately 19,000 years ago. Thereafter, glacier retreat began, largely ending by about 11,700 years ago. That marked the beginning of the Holocene interglacial geologic epoch, which continues to the present. During the last glacial period, sea level was much lower because so much water was locked up in ice sheets, largely at the poles. This lowering of the sea level exposed the margins of the continents (the continental shelves) around the world. When the Ice Age ended, sea level started to rise during the deglacial period, a process that continued into the Holocene. Deltaic regions received meltwaters from the thawing glaciers, along with glacier- derived sediments. Of particular note in the late Holocene is a climate episode called the Medieval Warm Period, originally identified by the English botanist Hubert Lamb. The Medieval Warm Period was a time of warm climate in the North Atlantic region and may have also impacted other areas around the world. It lasted from about the years 950 to 1250. Later in this chapter, I will discuss this climate anomaly, along with something called the “Hockey Stick” debate, which relates to exceptional warming during recent centuries of the Holocene (i.e., global warming). In any case, all modern and paleodeltas formed during periods of peak sea level in the Holocene. These new deltas had fertile soils that were constantly irrigated by the flow of fresh water, which promoted early settlement by humans. So, the Holocene started near the end of the retreat of the Pleistocene glaciers, and human civilizations arose entirely in the Holocene Epoch. To view the Holocene, simply look around you today. In this chapter, I will explore the natural and human-induced causes of global climate change and how they impact deltaic regions.