Newfoundland was affected by three different mountain-building periods: the Taconic at the end of the Ordovician period, the Acadian foldings in Devonian time and the Appalachian folding and faulting during Permian time after the Iast of coal measures had been laid down.
The surface is a series of even-topped plateaus which are interpreted as old erosion surfaces similar to those found in the Maritime Provinces. Here, also, they are found to rise toward the north indicating that there has been a deformation of the earth's crust since these surfaces were cut. There seem to be three of these old erosion levels or peneplains as they are often called. The highest and oldest is represented by the flat top of the Long Range at about 2,200 feet, the second is seen in the higher valleys at about 1,300 feet and on the residual hills or monadhocks, to the east of the range. The lowest and youngest of these erosion levels is the most widespread and comprises the most of the plateau-like surface of the island ranging from 500 to 1,000 feet in elevation.
As in the neighbouring mainland, the surface of Newfoundland is covered by unconsolidated deposits of variable depth and great complexity. There seem to have been at least two periods of glaciation and may well have been more because the country has been very incompletely examined. There is some controversy among geologists as to whether the great continental ice caps extended far enough to cover the island or whether it had its own local glaciers. The ice-carved valleys, the numerous lakes in rock-basins on the plateau and the rounded shapes of the residual rock hills all point to the existence of an ice age in fairly recent time.There have also been recent changes in sea level. This is particularly evident along the much indented northeast coast. This is similar to the southern coasts of Maine and Nova Scotia and is to be explained in much the same way, as the result of the recent drowning of river valleys which had become entrenched during the uplift of the old erosion surface. Some overdeepening may also be present due to the work of the glaciers. There is also evidence of recent uplift of the land in the presence of raised marina beaches in various parts of the island.
Newfoundland possesses many rivers, but being a very irregularly shaped island, few of them are very long. Since the plateau of Newfoundland is tilted toward the northeast, most of the important rivers flow in that direction. Those draining to the south coast are short and rapid.The largest river is the Exploits, 200 miles long, draining an area of about 4,000 square miles in the central part of the island. In its drainage basin are a number of lakes; Red Indian Lake, 37 miles in length, is the largest. Exploits River empties into the Exploits Bay, a long arm of Notre Dame Bay. Farther east, Gander River, 100 miles long, and Terra Nova River, 70 miles in length, drain large areas. Gander Lake, drained by the river of the same name, is about 33 miles long. In the western part of the island, the largest river is the Humber, 80 miles in length. In its drainage basin are Grand Lake, about 56 miles long and 200 square miles in area, and Deer Lake which is about 15 miles long. There are many smaller river systems. These streams are important as sources of power, and as means of transporting pulpwood from the interior. In addition, they contain salmon and trout which are popular with visiting anglers.
The coastline of Newfoundland is estimated to be 6,000 miles long, very long indeed for its area of 43,000 square miles. From the map it is very noticeable that there are three distinct types of coastline:
I. Rectilinear coasts such as those along both sides of the Northern Peninsula and along the western part of the south shore. Such straight lines are probably related to major fault zones of the earth's crust. Good harbours are rather few.
2. The very much indented northeast facing coast from White Bay to Bonavista Bay. This coast is bordered by a great number of small islands. Between them and the mainland, and among the islands themselves, is a veritable maze of waterways to which Newfoundlanders have applied a number of curious geographic names such as "tickle", "run", "reach", "arm" and "sound".
3. The embayments of Eastern Newfoundland. The eastern part of the island is composed of a number of peninsulas between which are very large open bays such as Trinity Bay, Conception Bay, St. Mary's Bay, Placentia Bay and Fortune Bay. The shape of this coast suggests its origin in the drowning of a very old mountain range. For the most part, the shores are steep and rocky but there are a few good pouchshaped harbours, among them St. John's, the chief port of the island.
The coast is geographically the most important part of Newfoundland. Most of the people are settled along the bays and inlets and the interior of the country is practically empty.