Quebec's highest point at metres is Mont d'Iberville, known in English as Mount Caubvick, located on the border with Newfoundland and Labrador in the northeastern part of the province, in the Torngat Mountains. The most populous physiographic region is the Saint Lawrence Lowland. It extends northeastward from the southwestern portion of the province along the shores of the Saint Lawrence River to the Quebec City region, limited to the North by the Laurentian Mountains and to the South by the Appalachians. It mainly covers the areas of the Centre-du-Québec, Laval, Montérégie and Montreal, the southern regions of the Capitale-Nationale, Lanaudière, Laurentides, Mauricie and includes Anticosti Island, the Mingan Archipelago, and other small islands of the Gulf of St. Lawrence lowland forests ecoregion. Its landscape is low-lying and flat, except for isolated igneous outcrops near Montreal called the Monteregian Hills, formerly covered by the waters of Lake Champlain. The Oka hills also rise from the plain. Geologically, the lowlands formed as a rift valley about 100 million years ago and are prone to infrequent but significant earthquakes. The most recent layers of sedimentary rock were formed as the seabed of the ancient Champlain Sea at the end of the last ice age about 14,000 years ago. The combination of rich and easily arable soils and Quebec's relatively warm climate makes this valley the most prolific agricultural area of Quebec province. Mixed forests provide most of Canada's springtime maple syrup crop. The rural part of the landscape is divided into narrow rectangular tracts of land that extend from the river and date back to settlement patterns in 17th century New France.