Big Idea 1: The Earth is a system of systems

The Earth is composed of many systems, which cycle and interact in both space and time. It is also part of a multitude of systems, nested in larger systems such as the solar system and the universe. Systems are composed of an untold number of interacting parts that follow simple rules; they can and do evolve. For example:

Outlining the geologic history of any region demonstrates the concept of the Earth as a system of systems. Plate tectonics drives the formation of mountains. Subsequent weathering and erosion of the uplifted mountains leads to the formation of deltas in the adjacent shallow seas. And with uplifted continents, shorelines change and the distribution of marine communities are altered.

The planet’s systems are intimately connected: the forces of one system affect other systems nested within it. As plates collide, systems that drive plate tectonics are obviously linked to the formation of mountains, but they are ultimately linked to and influence much smaller systems. The intense heat and pressure resulting from collisions can lead to the metamorphism of existing strata, or it can melt existing rocks to later form igneous rocks.

As glaciers extended down from the north, they cut into river valleys in the upper portion of the Midwest. This glacial system shaped the landscape, deepening and widening the river valleys and, after the glaciers’ retreat, triggering the formation of the Great Lakes. Had the glaciers never advanced so far south, the erosional forces that led to the formation of these lakes would have never been set in motion.

See Chapter 4: Topography for more on how glaciers shaped the Midwestern landscape.
Each of the remaining ideas operates across multiple systems within the larger Earth system.