NO. 23.] CENTRAL CONNECTICUT IN THE GEOLOGIC PAST. 37 



the Triassic, changes to a great fracturing of the crust which 

 spreads over Connecticut and along certain belts of the Appala- 

 chian system, especially involving the regions of previous move- 

 ment and deposition. In Connecticut the eastern and western por- 

 tions suffer relative uplift, and thus the central valley becomes out- 

 lined. The individual slices or blocks, many of which are miles 

 in width, are rolled partly over, and their fractured sides slip 

 past each other hundreds or even thousands of feet. The western 

 side of each block is tilted upward, but the eastern side drops 

 down relatively to the block next eastward. The faulting is a 

 progressive readjustment of the broken parts of a broad and 

 gentle arch whose crest lies west of the Triassic basin. Thus there 

 comes into being a new generation of mountains whose higher 

 summits again invade the clouds. 



Once more a period of comparative quiet prevails and millions 

 of years pass away. Erosion, working always toward the level 

 of the sea but never below it, planes across the tilted crust blocks, 

 and in southern New England bevels all alike, be they of softer 

 sandstones ribbed with harder trap, or of resistant metamorphic 

 rocks. The mountains once again vanish from central Connect- 

 icut, leaving hills a few hundred feet in height as the only surviv- 

 ing remnants, and Jurassic time draws in turn to its close. 



But nature never repeats herself, and the crust movements 

 which break earth history into periods are varied through the 

 course of ages. During the Paleozoic the chief lines of uplift had 

 been through New England, and to the south where in later geolo- 

 gic 'times are coastal plain and sea. Now at the close of the 

 Jurassic the new relation of the Applachians begins to be estab- 

 lished. A warping of the crust begins, but the axis of greatest 

 uplift is now farther inland, where, during most of the Paleozoic, 

 subsidence 2nd sedimentation had been the prevailing rule. To- 

 ward the margin of the continent, where formerly the Appala- 

 chians had risen to maximum heights, subsidence becomes mani- 

 fest. The sea seeks to advance inland, but the great volume of 

 river sediments from the regions of rising crust holds back the 

 strand-line and builds a wide stretch of delta land. Branching, 

 shifting rivers, spreading into swamps, weave an interlacing tangle 

 of waters through the low alluvial plains. Farther inland is a belt 

 of subdued but yet hilly country. Connecticut is divided between 



