Fossils are the remains of things that oncelived on Earth.In the next few slides you will see fossilsfound either in or near Fort Worth.Think about what these fossil remains ofanimals that lived 100 million years ago tell usabout what Fort Worth was like long ago.
Looking at these organisms, you canconclude they once lived:a. in a forest c. in a grasslandb. In an ocean d. in a desertYes, you could conclude that they oncelived in an ocean.So what must have been here in Fort Worthat that time (100 million years ago)?Yes, at one time, very long ago, this areawas covered by a shallow sea.
The North American continent during late Cretaceous time.The Western Interior Sea covered most ofthe Midwest from the present Gulf ofMexico to the Arctic.
Fossils of animals that lived in the sea can befound all throughout the western UnitedStates and Canada. Colorado Utah Texas More evidence for what?
Yes, more evidence for that ancient inland sea. Wikipedia CommonsWestern Interior Seaway during the mid-Cretaceous, about 100 million years ago.
But then you might have noticed that the areas in Colorado and Utah where the fossils are found are now mountains. So somehow that flat seabed where the sea creatures of long ago lived is no longer flat—it is a chain of mountains. So something else must have happened.Yes, after the inland sea, forces deep insidethe Earth pushed up the flat seabed intohuge mountains.
And right now, a new mountain range is beingbuilt in the middle of the Atlantic Ocean asmagma flows from the mantle onto the oceanfloor.Hundreds of millions of years in the future, a tallmountain chain will rise above the sea.
So over time, does the surface of theEarth stay the same?What does happen?The forces of nature constantly arechanging the surface of the Earth creatingnew landforms and destroying others.Usually these changes take a very, very longtime-- tens of thousands, hundreds ofmillions of years. Once in a while theyhappen very quickly like an earthquake orlandslide or some volcanic eruptions.