BBC Men of Rock 3 of 3 The Big Freeze

The video begins with a scenic view of Scotland's ancient landscape, which is deeply connected to the planet's geological history. It introduces the audience to the idea that Scotland's epic and violent past holds keys to understanding Earth's mysteries through the work of pioneering scientists.

Two scientists, Louis Agassiz and William Buckland, explored these landscapes 200 years ago to understand the geological formation of the Highlands. Agassiz, inspired by his experiences in the Swiss Alps, developed a revolutionary idea about Earth's past ice ages by studying glaciers and their effects.

Agassiz observed glacier movements and how they carried large boulders, leading to a groundbreaking theory that ice once covered large parts of Europe. His experiments showed glaciers acted like 'rivers of ice', shaping the landscape by transporting rocks and debris.

In Scotland, Agassiz sought evidence of his ice age theory by examining geological features such as "erratic" boulders and U-shaped valleys, similar to those found in the Alps, to demonstrate that glaciers had once dominated the region.

The Glen Roy landforms posed a major geological mystery until Agassiz proposed they were ancient shorelines of glacier-made lakes. This crucial evidence supported his theory, suggesting vast ice sheets once covered Scotland, carving out its dramatic landscapes.

Despite Agassiz's findings, his ice age theory faced skepticism. His observations received little immediate support because of prevailing beliefs that Earth's climate had remained largely stable over time, a view strongly defended by influential geologist Roderick Murchison.

James Croll, a janitor at Anderson College, proposed a theory linking Earth's orbital changes to climate fluctuations, explaining the occurrence of ice ages. His ideas about astronomical cycles as drivers of climate were initially overlooked but later recognized as groundbreaking.

Croll suggested Earth's elliptical orbit periodically brings it farther from the Sun, cooling the planet and allowing ice sheets to grow—an effect amplified by the reflective properties of ice (albedo effect), helping explain the occurrence of extensive ice ages.

Croll's ideas laid the groundwork for understanding the natural cycles of ice ages, predicting multiple glaciations in Earth's past. These concepts were crucial for later developments in climate science, although Croll himself initially lacked widespread recognition.

Later scientific developments verified Croll's theory using ice core samples, aligning geological evidence with his astronomical cycles and proving the Earth's climate experiences regular, predictable ice ages.