MONTPELIER, Vt. (AP) – A 71-acre site on Lake Champlain that contains sections of what is believed to be the world’s oldest reef in which coral has been found will be preserved and opened to the public under an agreement announced Tuesday.

The Chazy Reef on Isle La Motte was formed about a half billion years ago from a warm shallow sea south of the equator. Over the eons the entire area moved north to its present location.

“These rocks are 450 million years old or so,” said Charlotte Mehrtens, the chair of the geology department at the University of Vermont. “You can walk through time seeing how the layers are composed of different animals. That sequence is beautifully exposed in Isle La Motte.”

Two preservation groups announced Tuesday they have bought a 71-acre parcel of land on Isle La Motte known as the Goodsell Ridge. It will be added to the existing 10.3 acres of the already preserved and adjoining Fisk Quarry. The area will enable visitors to get a glimpse into hundreds of millions of years of geologic history, said Linda Fitch of the Isle La Motte Preservation Trust.

“One scientist called it a time capsule of reef building,” said Fitch. “On Isle La Motte you can see how it evolved from simple little mounds into what I call a reef city.”

The Isle La Motte Trust and The Lake Champlain Land Trust have spent the last three years raising the money to buy the parcel located in the middle of the 7-mile by 3-mile island at the northern end of Lake Champlain. The purchase price was not disclosed.

The land will become a scenic area that will include an outdoor museum and fossil preserve. There will be interpretive trails. A visitors’ center in an old farmhouse will provide informational displays.

Fitch, whose family has owned property on Isle La Motte since 1970, first became aware of the geological history of Isle La Motte about a decade ago when a geology teacher asked her for permission to take his class onto her land. Fitch tagged along.

Even though she didn’t understand much of the science, Fitch started looking for a way to preserve the Fisk Quarry, named for the family that owned the land a century ago. The deal to buy the land from a businessman who wanted to re-open the quarry was completed in 1999. Since then about 3,000 people a year have visited, Fitch said.

The reef, part of which now lies exposed in Isle La Motte, was created when what is now North America was lying south of the equator, Mehrtens said. There the conditions for the creation of a reef – warm, moving water – were perfect.

The earliest sections of the reef were made up of organisms that predate modern coral by millions of years, although more modern coral can be found in some of the newer recent sections of Isle La Motte, Mehrtens said.

She said the area demonstrated the way reefs evolve in the same way that a forest that has been destroyed by fire will regenerate first with weeds, and then more complex plants and ultimately oak trees.

“The animals adapted over time,” she said. “Many people consider this to be one of the oldest examples of the biological principle of succession.”

The original reef stretched for 1,000 miles. Portions of that reef can still be seen and Mehrtens has studied other portions of it from Newfoundland to Tennessee. But Isle La Motte is the only place where so much of the sequence is visible, she said.

Mehrtens frequently brings her classes to study and scientists from across the world visit regularly as well. She said Fitch had made sure it will continue to be available to the public.

“They’ve ensured this will be available to Vermont students well into the future,” she said. “This also has the potential to be the equivalent of being sort of an ecology destination for people who are interested in studying these kinds of rocks, or the history of life or the history of Vermont.”