The landscape we see at the surface of the Earth is a function of the interactions between internal and external processes. The earth systems approach of geology considers the planet as a whole, including rocks and rock formation, surface processes, oceans and atmospheres, and all natural resources. The study of the geologic theories about continental drift, and the observations that led to the development of plate tectonic theories show a dynamic and interactive level of the ecosystem often over-looked.
Before the dawn of modern geology in the 19th century, many people believed that Earth had been formed by catastrophes. The idea was that incredible events – huge volcanic blasts, floods, violent winds - swiftly built our planet. That theory, now discredited, is known as catastrophism. Most problems are far more accurately described by the newer theory of "uniformitarianism," which holds that Earth was made by the same forces we see today – the trickle of rain, the polishing of wind, the creep of continents – working steadily through unimaginable depths of time.