4th grade Social Studies

Standard I

Objective 1

To examine the climate changes that caused Utah to have its current physical geography, view this slide presentation from Davis School District.

PALEOZOIC

Paleozoic

During this era Utah was on the coastline of an ocean. If you lived in Davis County at this time you would live underwater, just off the beach! Coral reefs formed nearby. These ancient reefs are now limestone in the Wasatch Mountains.

EARLY JURASSIC

At this time the oceans had moved far from Utah. Most of our state was a desert with blowing sand dunes. These sand dunes hardend into the rock formation we now call Navajo Sandstone. You can see these ancient dunes – now rock – in Zion National Park and around St. George, Utah.

LATE JURASSICThis is the time of dinosaurs! Now Utah is hot and swampy. There are volcanoes in the west and northwest and rivers and lakes in the east and southeast. This is a perfect home for the dinosaurs and they are abundant in the state. Their bones have been found in great numbers at Dinosaur National Monument.

LATE CRETACEOUS

Western Utah is now mountains and eastern Utah is a giant inland sea. There are still plenty of dinosaurs in Utah at this time. Giant forested swamps formed along the edges of this sea. When these forests fell down and were buried they became Utah’s coal. We mine it today.

PALEOCENE

During this time period the Uinta Mountains, the Colorado Plateau, and the Rocky Mountains have all begun to rise and appear. The dinosaurs are mostly all gone. A large, freshwater lake covers much of the central portion of our state.

EOCENE

A giant lake fills up in the area that will eventually become the Uinta Basin. For this reason, we call this ancient lake Lake Uinta. The accumulations that formed on the bottom of this lake have become the source of Utah’s oil shales. Also, this is why it is fairly easy to find fossil shells in this area today!

OLIGOCENE

Volcanoes emerged in portions of western Utah. Smaller lakes (which would be considered huge today) formed across Utah.

MIOCENE

The North American continent began to stretch westward during this time and magma seeped up through the cracks into Utah. Minerals brought up with the magma formed the deposits of gold, silver, copper, and other things we mine in our mountains today.

PLEISTOCENE

This is the time period we call the “Ice Ages.” The geography of Utah was very similar to what it is now. The climate at this time was wetter and colder and there were glaciers in Utah’s mountains. A giant fresh water lake called Lake Bonneville formed and covered much of the state. The beaches along the edges of the lake are the sandy benches and foothills of our mountains today.

PRESENT

All that is left of Lake Bonneville is the Great Salt Lake. There are other things left from earlier periods, however. The oil shales of the Uinta Basin, the mineral deposits of the mountains, and the red-rock sandstones of ancient sand dunes are examples of Utah’s geologic past.