Glaciers in Past Ice Ages

Summary

This lecture discusses glaciers and past ice ages, highlighting Earth's climate history, including periods of glaciation and interglacial warm spells. It covers the Pleistocene epoch, when nearly a third of Earth's surface was covered by glaciers, and the resulting landscape features like paleolakes. The lecture also touches on crustal depression and post-glacial rebound, explaining how the weight of glaciers impacts the Earth's crust. Additionally, it explores the connection between glacial retreats and rising sea levels, noting that during the peak of the Pleistocene Glaciation, global sea levels were 400 feet lower than today.

Takeaways

• 😀 Paleoclimatology is the study of Earth's past climates and the history of ice ages, which are cold periods lasting millions of years, interrupted by brief warmer phases.
• 😀 Earth experiences alternating cooler and warmer periods, with glacial and interglacial phases influencing human history, such as the Viking colonization during the Medieval Warm Period.
• 😀 The Pleistocene period, beginning 2.6 million years ago and ending about 12,000 years ago, saw large portions of Earth covered by ice sheets and glaciers, including most of Canada and Northern Europe.
• 😀 During the Pleistocene, periglacial landscapes extended much further than today, covering twice the area and indicating a much colder Earth.
• 😀 Ice sheets during the Pleistocene reached thicknesses of up to one mile or more in certain regions, leaving behind landscapes marked by Paleolakes and other features.
• 😀 Deep sea cores and ice cores in Antarctica provide crucial data about the Earth's temperature during the ice ages, helping scientists reconstruct past climates.
• 😀 As glaciers receded, they left behind various landscape features like Paleolakes, particularly in the American West, where large lakes such as Lake Bonneville and Lahontan once existed.
• 😀 Paleo lakes were not solely formed by receding glaciers, but also by wetter climates historically, which contributed to their formation and filling.
• 😀 Crustal depression occurs when the weight of glaciers pushes down Earth's crust, and over time, post-glacial rebound leads to the crust rising back up.
• 😀 Global sea levels were much lower during the peak of the Pleistocene Glaciation, with levels about 400 feet below today's sea level due to the large volume of water stored in glaciers.

Q & A

What is paleoclimatology, and why is it important for understanding glaciers and ice ages?

Paleoclimatology is the study of Earth's past climates. It is important for understanding glaciers and ice ages because it helps us track the historical climate changes that led to periods of glaciation and interglacial warmth, providing insight into how Earth's climate system operates over long timescales.

What is an ice age, and how long can it last?

An ice age, or glacial age, is a cold period in Earth's history that can last several million years. These periods are marked by the presence of large ice sheets covering significant portions of the Earth.

What are interglacial periods, and how do they relate to ice ages?

Interglacial periods are brief warm spells that interrupt ice ages. They represent times when the Earth's climate is warmer, allowing glaciers to retreat. The alternation between glaciations and interglacials plays a significant role in Earth's climate cycles.

How did the Pleistocene period contribute to the Earth's glacial landscape?

The Pleistocene period, which began about 2.6 million years ago and ended around 12,000 years ago, was characterized by the widespread coverage of Earth's surface by ice sheets and glaciers. This period significantly shaped landscapes, including the formation of large lakes and distinctive periglacial features.

What are periglacial landscapes, and how did they change during the Pleistocene?

Periglacial landscapes are regions found at the margins of glaciers that are affected by freeze-thaw processes. During the Pleistocene, these landscapes covered twice the area they do today, indicating a much colder Earth with widespread glaciation.

What was the impact of glaciation on sea levels, and how did they change over time?

During periods of glaciation, global sea levels were much lower due to the large volume of water locked in glaciers. At the peak of the Pleistocene glaciation, sea levels were 400 feet below today's levels. As the glaciers retreated, sea levels rose, contributing to the current global sea level.

What are paleo lakes, and how are they related to glaciers?

Paleo lakes are ancient lakes that existed during past glaciations, often formed by the melting of glaciers. The retreating glaciers left behind water-filled basins, creating these lakes, which are found on every continent except Antarctica.

What was the role of wetter climates in the formation of paleo lakes?

In addition to glacier retreat, wetter climates played a significant role in filling paleo lakes. Historical periods of increased rainfall contributed to the expansion and formation of these lakes, especially in regions that were not entirely covered by glaciers.

How did crustal depression occur during glaciation, and what effect did it have on the Earth's surface?

Crustal depression occurred due to the immense weight of the ice sheets, which caused the Earth's crust to sink or 'depress' under the pressure. Over time, as the glaciers melted, the crust began to rebound, a process still observable in regions like Canada and Northern Europe.

How does post-glacial rebound continue to affect Earth's surface today?

Post-glacial rebound is the slow process by which Earth's crust adjusts after the melting of glaciers. This rebound continues to affect the Earth's surface today, especially in regions that were once heavily covered by glaciers, such as parts of Canada and Northern Europe, where the crust is still rising.