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A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized rugose coral, Hexagonaria percarinata. [1] Such stones were formed as a result of glaciation, in which sheets of ice plucked stones from the bedrock, grinding off their rough edges and depositing them in the northwestern (and some in the northeastern) portion of Michigan's lower peninsula.
Volcanic strata protrude at Isle Royale and the Keweenaw Peninsula [9]. Lake Superior occupies a basin created by the rift. [3] Near the present lake, rocks produced by the rift can be seen on the surface of Isle Royale and the Keweenaw Peninsula of the Upper Peninsula of Michigan, [9] northwest Wisconsin, [10] and on the North Shore of Superior in Minnesota and Ontario. [4]
The Marquette Iron Range is a deposit of iron ore located in Marquette County, Michigan in the United States. The towns of Ishpeming and Negaunee developed as a result of mining this deposit. A smaller counterpart of Minnesota's Mesabi Range , this is one of two iron ranges in the Lake Superior basin that are in active production as of 2018.
[8]: 1 Penokean-age rocks in the northern Wisconsin and the Upper Peninsula of Michigan contain areas of low-pressure, low- to high-temperature metamorphism. [ 8 ] : 3 The folding and metamorphism increased in intensity to the south and southeast, [ 8 ] : 1 and produced the isolated gneissic 1,755-million-year-old [ 2 ] : 342 Watersmeet Domes ...
On a map showing only metamorphic rocks, the Canadian Shield forms a circular pattern north of the Great Lakes around Hudson Bay.. The Canadian Shield is a large area of Archean through Proterozoic igneous and metamorphic rocks in eastern Canada and north central and northeastern United States.
Igneous rock (igneous from Latin igneus 'fiery'), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.
Igneous rocks injected millions of years later form a marbled network through parts of the Colorado Plateau's darker metamorphic basement. [11] Cedar Mesa Sandstone forms the Druid Arch, in Canyonlands National Park. These deeply-formed rocks were uplifted, eroded, and exposed for eons.
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