LGLC Discovery Series hike explores Adirondack Geology

Colliding land masses, churning hot magma and mile-thick glaciers were the topic of a Lake George Land Conservancy hike up The Pinnacle in Bolton on Saturday, May 18. The hike is part of the Conservancy’s Discovery Series, an educational program of themed hikes led by an Up Yonda naturalist. The program is presented by the Conservancy and Up Yonda Environmental Education Center.

 “We are going to skip through time as we go,” said Environmental Educator Rick Landry as he led hikers from The Pinnacle trailhead into the forest. A billion years ago, he told the group, all the major land masses began coming together, a mountain-building event called the Grenville Orogeny. Half a billion years ago the land began stretching and 20 million years ago hot magma pushed its way up and created a dome underneath the Earth’s surface where it then cooled. That dome is the Adirondack Mountains.

“Some of the oldest rocks we find in the world are found right here in the Adirondacks because these rocks have actually been pushed up by activity underneath,” says Landry. “A lot of the rock that we find up here in the Adirondacks is granite.” Granite is an igneous rock that is formed when magma cools.

Along the trail, Landry stopped at a boulder and identified it as a Hudson Bay Rock, an erratic, carried from the north and dropped in Bolton by a glacier. Hikers also had the opportunity to observe spring woodland flowers in bloom, a variety of insects, millipedes, and, in the muddier sections of the trail, juvenile newts.

At The Pinnacle Summit, which overlooks Lake George, Landry explained how glaciers created the Queen of American Lakes. Lake George was once two rivers. One flowed north from The Narrows to La Chute, Lake Champlain and the St. Lawrence River, and one flowed south from The Narrows to the Hudson River.

“As these glaciers pushed their way south, they were carrying all kinds of sediment with them, and it’s like this big conveyor belt,” says Landry. As wintertime snow decreased and summer melt increased, the glaciers began to recede, pausing and dropping sediment over what is now the lake’s Southern Basin.

Sediment deposits formed glacial moraines that acted as dams, allowing water running down the mountains to pool and form the lake. Landry pointed southeast across the lake to a rise in the landscape, Pickle Hill Road in Queensbury, and identified it as a glacial moraine. Rises are also found near Queensbury’s Rush Pond and Glen Lake. The peninsulas and islands of Lake George are all glacial deposits.

Throughout the hike, Landry stressed the importance of caring for the land that surrounds Lake George. “Everything that happens on these lands impacts this lake right here.” Creating “social trails,” hiker-created detours off the official, maintained trail, contribute to erosion that allows more sediment to flow into the lake. Along the trail, the group noted several “social trails” off the sides of the path, and Landry laid fallen tree limbs across them to discourage their use.

Upcoming Discovery Series hikes include Intro to Hiking, Beginner Birding, Beavers, and Changing Trees. The Discovery Series hikes are free. Advanced registration is required. Visit the LGLC website for a list of hikes and registration information. The Discovery Series is sponsored by the Town of Bolton and the Lake George Mirror.