central and southern Green Mountain range include the oldest rocks in Vermont, formed about one billion years ago during the first mountain building period (or orogeny). Subsequently, about years ago, the second mountain building period created Green Mountain peaks that were tall, three to four times their current height and comparable to the Himalayas. The geological pressures that created those peaks remain evident as the Champlain Thrust, running north–south to the west of the mountains (now the eastern shore of Lake Champlain). It is an example of geological fault thrusting where bedrock is pushed over the newer rock formation. As a result of tectonic formation, Vermont east of the Green Mountains tends to be formed from rocks produced in the Silurian and Devonian periods, and western Vermont mainly from the older Pre-Cambrian and Cambrian material. Several large deposits within the state contain granite. The remains of the Chazy Formation can be observed in Isle La Motte. It was one of the first tropical reefs. It is the site of the limestone Fisk Quarry, which contains a collection of ancient marine fossils, such as stromatoporoids, that date to years ago. At one point, Vermont is believed to have been connected to Africa (Pangaea); the fossils found and the rock formations found on the coasts in both Africa and America are evidence affirming the Pangaea theory. In the past four centuries, Vermont has experienced a few earthquakes, rarely centered under the state. The highest ranked, in 1952, had a Richter magnitude scale 6.0 and was based in Canada. Fauna The state contains 41 species of reptiles and amphibians (including the spring peeper), 89 species of fish, of which 12 are non native; 193 species of breeding birds, 58 species of mammals (including black bears, eastern chipmunks, coyotes, fishers, red and gray foxes, porcupines, and woodchucks), more than 15,000 insect species (including luna moths), and 2,000 higher plant species, plus fungi, algae, and 75 different types of natural communities. Vermont contains one species of venomous snake, the timber rattlesnake, which is confined to a few acres in western Rutland County. Wildlife has suffered because of human development of the state. By the mid-19th century, wild turkeys were exterminated in the state through overhunting and destruction of habitat. Sixteen were re-introduced in 1969, and had grown to a flock estimated to number 45,000 in 2009. In 2013, hunters killed 6,968 of these. Since 1970,