These are geological processes that took place outside the earth

Earth’s surface is the arena for most life and all human activity, yet what lies beneath our feet is as mysterious as it is familiar. Earth scientists or not, we recognize hills, mountains, glaciers, deserts, rivers, wetlands, and shorelines. If a good deal of rain falls, floods may occur; if a storm strikes the coast, the beach may erode; if we are careless with our soil, we may damage or even lose it. These ideas are well known, but with just a few questions we arrive at the edge of our knowledge and face gaps that matter to our safety, our food and water security, the infrastructure of roads and river navigation, and the survival and diversity of ecosystems and services they provide.

Any familiar landscape illustrates the point. Start with a stream channel and ask a series of simple questions: What controls its size, pattern, and magnitude of flooding? What plants and animals live in and along this stream, and how do biological processes—including human activities—affect the downstream flow of nutrients and water? Next, look about and wonder how this stream relates to its valley and the surrounding hillslopes. How did these landforms arise, and how are they related to one another? Why are hillslopes usually mantled with soil, and why is that soil so much richer and more complex than simple ground bedrock? In addition to landforms and their mantling soil, landscapes host a set of interconnected ecosystems, both visible and microscopic. How have these ecosystems shaped and been shaped by Earth’s surface? How is the flow of nutrients that nourishes ecosystems connected to the landscape? Finally, if we take the longest view, our stream is part of a network that forms a kind of continental circulatory system, carrying water, sediment, nutrients, and biota from high ground to low-lying coastlines. How did this system come to be, how long has it existed, and how is it related to climate (modern and past) or to the tectonic forces that shape continents? How will it behave in the future, and how do human activities influence that behavior