94 



(c) Spiders, scorpions, myriopods 1 , land snails. 



(d) Dragon flies, cock roaches, crickets, beetles; no bees, no 



flowers. 



(e) Sharks, ganoids. 



(f) First terrestrial vertebrates amphibians. 



II. Subsequent Events. 



1. Subsidence: Shallow Sea, Unstable. 



2. Life Submerged. 



3. Deposition of Sediment. 



4. Generation of Heat. 



5. Metamorphosis of Plants. 



III. Stratification of Coal Measures. 



1. Successive Layers of Clay and Coal. 



2. Layers Vary in Thickness. 



MINERAL OIL AND GAS. 

 I. Deposits. 



1. Porous Rock Trenton Limestone. 



2. Reservoir Capped by Impervious Layer of Rock. 



II. Origin. 



1. Decomposition of Animal and Plant Life, Deposited in Seas and 



Lakes. 



2. Slow Distillation Caused by Pressure and Heat. 

 '*. Hydrocarbons Produced. 



4. Hydrocarbons Exist as Gas or Oil. 



GLACIAL PERIOD. 



I. Glaciated Area of North America. 



1. Canada, Greenland. 



United States, from Atlantic Ocean west, north of Ohio and Mis- 

 souri Rivers. 



2. Kinds of Glaciers. 



(a) Continental Greenland. 



(b) Valley Western United States. 



(1) Snow fields, accumulation of snow. 



(2) Neve granular ice. 



(3) Ice stream moving compact ice. 



3. Moraines. 



(a) Lateral a moving talus. 



(b) Medical formed by union of two lateral moraines. 

 (c} Terminal accumulation at front end. 



(d) Ground loose rock, material beneath the ice. 



