Final answer:
It is false to claim that igneous rocks have never formed in Missouri. Both extrusive and intrusive igneous rocks are present in Missouri, indicating a history of volcanic activity and magma crystallization.
Step-by-step explanation:
The statement that igneous rocks have never formed in Missouri is false. Missouri, much like other regions around the world, has a geological history that includes the formation of igneous rocks. These rocks are classified into two main types: intrusive (plutonic) and extrusive (volcanic) igneous rocks. Extrusive igneous rocks are formed from lava that cools rapidly on the Earth's surface, resulting in a fine-grained texture due to the fast cooling that leaves no time for large crystals to grow. Contrarily, intrusive igneous rocks form from magma that cools slowly beneath the surface, leading to a coarse-grained texture.
In Missouri, the igneous rocks typically found are, in fact, of both types. For example, granites and rhyolites in Missouri are evidence of ancient volcanic activity and crystallization of magma within the earth's crust. Thus, to evaluate different provinces, geologists consider plutonic and volcanic rocks separately, mainly due to their different cooling ages, which tell us about the geological history and processes that occurred in those regions.
In conclusion, it is false that igneous rocks have never formed in Missouri; both extrusive and intrusive types are found in state's geological record.