FERNS, FOSSILS AND FUEL 
The early part of the Tertiary period is called the 
Eocene. It was followed by the Miocene, which fills the 
middle portion of the Tertiary. It was a period of great 
volcanic activities in North America, Europe, and Asia. 
The southern Alps and the Himalayas were formed dur¬ 
ing the Miocene, and the Rocky Mountains were raised 
from a much lower to their present high level. During 
the period great volcanic eruptions took place in the 
western portion of North America, mainly in Washington 
and Oregon. A great many plants were buried in the 
lava and the outlines and venations are beautifully pre¬ 
served in the volcanic tuffa. 
Near the town of Florissant, Colorado, is one of the 
richest fossil plant deposits of the Miocene. At that 
time a small lake existed there in the midst of granite 
hills. At the bottom of this lake a deposit of thin shales 
was formed, largely of volcanic ashes. Many thousands 
of plant fossils, belonging to at least two hundred and 
fifty species, have been found there, as well as thousands 
of insects, remains of fishes, feathers of birds, and shells. 
When we restore the vegetation which lies buried in the 
Florissant shales, we find a large variety of plant types 
ranging from small mosses to the largest trees of the 
time. Conifers like the pine and the juniper were con¬ 
spicuous. There flourished, along the shores of the 
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