YELLOWSTONE Trailside Notes (Number Two)

For the profitable enjoyment of Yellowstone the visitor should note the following:

1. Many times this part of the continent has been submerged.

2. During submergence layers of sediment gathered on the floor of the ocean—certain of these layers became hardened into rock.

3. After long ages these rocks slowly emerged and finally rose high above the sea level. Their folded layers we call the Rocky Mountain System.

4. During and since their period of elevation, volcanic activity and erosion have taken turns in modeling the landscape as we see it about us.

5. Terrific explosions have thrown out great quantities of volcanic material, (Tuff, Agglomerate, Breccia, etc.) and out of cracks and fissures molten rock has repeatedly flowed over the surface and even penetrated between the layers above mentioned and hardened into solid rock (Basalt, Rhyolite, Dacite, etc.).

6. The deeper masses of rock are still hot.

7. More recently, ice—in places several hundred feet in thickness—covered the entire area. Glaciers moved down the valleys, widened the walls and on melting left many evidences of their craftsmanship.

8. Hot water and gases rising from the—at first molten and then cooling—material on reaching the surface, gave up and are still giving up the substances held in solution, depositing them around their respective vents and thus forming terraces, cones, etc.

9. Throughout the processes above enumerated water and other agencies have been industrious and still are industrious in eroding the surface and in producing the landscape as it is today.

YELLOWSTONE FALLS