Book Description

Excerpt from Ferns and Flowering Plants of Isle Royale, Michigan After the formation of the lava beds, this area passed through a period during which there was an elevation Of the rock strata, erosion, depression, depositions Of new material, then elevation, tilting, and faulting, all Of of which resulted in the formation Of long narrow ridges with intervening valleys, which lie parallel to the long axis of the island. The rock strata were tilted toward the south shore of Lake Superior, and the degree Of tilting varies from 9° to 43° in various places. Then softer strata dis integrated, leaving the truncated ridges with gentle slopes on the southern side and with abrupt, steep slopes on the northern side. The ridges are mainly flat-topped, and the mam one, commonly called the Greenstone Ridge, is a divide which extends in the center and for the entire length of the island. This is broken into low gaps in three or four places. On this ridge there are three places which have an elevation above 500 feet according to contours drawn by Lane in 1908. Unpublished studies of George M. Stanley show that the highest portion Of the Greenstone Ridge is on the southwestern part Of the island and has an elevation close to 800 feet above lake level. Near the north shore Of the island is another ridge, the Minong Trap Ridge, which extends nearly the length Of the island and is above the 300-foot contour line. South of the Greenstone Ridge is a ridge which is much broker} but contains many points reaching above the 300-foot level. In addition to these main ridges there are many smaller intervening ones. Drainage is mostly parallel with the ridges. Some of the small streams in the intervening valleys empty into Lake Superior at the northeastern end, and others flow to the southwestern end. A few streams flow crosswise of the island in low gaps. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.