With two exceptions each of the large moraines incloses a lake. In this way Phelps, Taggart, Bradley, Jenny, Leigh, and Jackson Lakes originated; all ranged along the western border of Jackson Hole. No lakes were formed along the eastern border, inasmuch as on this side no glaciers extended beyond their canyons. String Lake is dammed in part by a gravel fill. Outwash plains are the deposits formed by streams which, during the Ice Age, issued from the glaciers. Of this origin are the broad, cobble-strewn flats, usually overgrown with sage, which cover the floor of Jackson Hole. They are diversified by bars, abandoned stream channels, terraces and "pitted plains", features of exceptional interest to one who examines them in detail. Several isolated buttes--Signal, Blacktail, and the Gros Ventre Buttes--rise like islands a thousand feet or more above these flats. [Illustration: PROFILE OF THE YELLOWSTONE-GRAND TETON REGION] Each canyon gives evidence of the vigor with which the glacier it once contained gouged out its channel. In many places the rock of the broad floors and steep sides is still remarkably polished. Every canyon leads up to one or more amphitheaters, or cirques, with sheer bare walls hundreds of feet high. Tracing these ice-gouged canyons headward one will discover many rock-rimmed lakelets, some hung on precipitous mountain sides where one might be pardoned for asserting that no lake could possibly exist. [Illustration: A CREVASSE IN TETON GLACIER _Crandall photo._] [Illustration: WINTER SCENE IN THE TETONS _Copyright, Crandall._] TRAILS An unbroken wilderness a few years ago, the Grand Teton National Park is now penetrated by some of the finest trails in the national-park system. These trails, suitable alike for travel afoot or on saddle horses, are 3 to 4 feet wide, free of boulders, and of grade so moderate they may be followed by old or young with full safety and a minimum of physical exertion. While the trails are traversable during the greater part of the summer, some of them may be blocked by snow early in the season. Those visitors expecting to climb the high trails should inquire at park headquarters or the office at the museum at Jenny Lake for information regarding the condition of the high trails. =_The Lakes Trail_= runs parallel to the mountains, following closely the base of the range and skirting the shore of each large body of water from Leigh Lake at the north to Phelps Lake at the south. It makes accessible the most important lakes, canyons, and peaks of the park, and is naturally the one from which all expeditions into the range begin. One can encircle by trail either Jenny Lake or String Lake, the hike around the former being one of the most popular in the park. =_The Canyon Trails_= described below are spur trails extending westward from the Lakes Trail, back into the most rugged areas in the Teton Range. Intervening canyons have been left in their splendid wildness.