Igneous rock the partial melting of rocks within the mantle and crust. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. Hence such rocks are smooth, crystalline and fine-grained. Basalt is a common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus. Some kinds of basalt solidify to form long polygonal columns. The Giant's Causeway in Antrim, Northern Ireland is an example. The molten rock, with
Geological Survey of Canada conduct fieldwork in the early 1950's . Dr. Alice Wilson, the first of these women, lobbied for the inclusion of paleontologist Frances Wagner shortly afterward. Around this same time, the GSC employed a third woman Dr. Helen Belyea. The Canadian National Seismograph Network is monitored by the Geological Survey of Canada. The Geological Survey Canada operates a network of 14 magnetic observatories throughout Canada, located as follows: Notes Bibliography Geological Survey of Canada The Geological Survey of Canada (GSC; ) is a Canadian federal government agency responsible for performing geological surveys of the country, developing Canada's natural resources and protecting