The Earth is an open system. Energy flows and cycles through the system; matter cycles within it. This cycling is largely driven by the interaction of the differential distribution of solar radiation and internal heat: the constant flow of solar radiation powers much of Earth’s ocean and atmospheric processes on the surface of the system, while the flow of heat from radioactivity within the Earth drives plate tectonics. For example:

One of the fundamental processes known to Earth system scientists is the rock cycle. The rock cycle illustrates the steps involved in the formation of one type of rock from another. It is a system that has operated since the Earth’s origin, and it continues today. The energy that drives weathering and erosion, melting, or an increase in heat or pressure, drives the continuation of the rock cycle.

The landscape we see today in the Southwest has been shaped by the geologic forces of the past, and these forces are still active today. Evidence throughout the Southwest’s terrain tells a story that began billions of years ago with the formation of tectonic plates, and this story continues to evolve. The movement of Earth’s plates is driven by plate tectonics, illustrating how the flow of energy drives the cycling of matter—the flow of heat from radioactivity within the Earth drives plate tectonics. Through geologic time, the Southwestern US has been shaped by the collision of the North American Plate with the Pacific Plate in a process driven by convection within the mantle. In addition to tectonic processes, energy flows and cycling matter also shape the landscape through erosion, deposition, sea level change and the direct action of humans.

In the recent geologic past, the Colorado River’s water has moved a tremendous mass of sediment from the interior of North America into the Gulf of California. Other Southwestern rivers, including the Rio Grande, Brazos, and Mississippi (through major tributaries like the Arkansas and Red), have moved great quantities of sediment to the Gulf of Mexico. The flow of sediment is, of course, driven by the water cycle, and, especially for the Colorado River, greatly affected by human activity. Like the rock cycle, and plate tectonics, the water cycle is convection driven. Without convection, Earth would be extraordinarily different, if it were here at all.