 Welcome back to our exploration on sedimentary rocks. In this video, we're going to take a deep dive into how geologists use sedimentary rocks to unravel the past. Let's get started. Sediments, size, sorting, and roundness are all indications on how far an individual sediment has traveled. How cool is that? A geologist can pick up a piece of rock and based on these three characteristics determine how far those sediments each traveled from its existing source when it broke off a piece of rock to getting to where it was deposited. As you can imagine, something that's quite large is a lot heavier so it takes a lot more energy to move so it's more likely to be deposited closer to where it was sourced from. Whereas you take something fine like a little piece of mud, it can be transported a long way in relatively slow-moving waters. If any of you are from Brisbane, consider the Brisbane River, which rather than a beautiful blue pristine river like you might picture is quite brown and murky. This means it is filled with mud and has been transported a long way. It will eventually be taken out to the ocean, transported even further away from its source. You take these two end members, something big and heavy, deposited close to its source and something small and light can be deposited a lot further away from its source. So moving on from size, let's talk about sorting.