12-10+Notes

· Although volcanic eruptions can be among the most violent and spectacular events in nature and therefore worthy of detailed study, most magma is emplaced at depth. · All form out of view beneath Earth’s surface, they can be studied only after uplifting and erosion has exposed them. · The structures that result from the emplacement of igneous material are called Plutons · Plutons are known to occur in a great variety of size and shape. · Intrusive igneous bodies are generally classified as tabular or massive by their orientation with respect to the host rock. · Plutons are said to be discordant if they cut through existing structures · Plutons are concordant when they form parallel to features like sedimentary strata · Plutons are closely associated with volcanic activity. · Dikes are tabular discordant bodies that are produced when magma is injected into fractures · The force exerted by the empaced magma can be great enough to separate the walls of the fracture further. · Most dikes are a few meters thick and extend laterally for no more than a few kilometers · Dikes are found in groups that served as vertically oriented pathways followed by molten rock that had lava flows · Dikes weather more slowly than surrounding rock · Sills and laccoliths are concordant plutons that form when magma is intruded in near-surface environment. · Sills are tabular plutons formed when magma is injected along sedimentary bedding surfaces · Because of their relatively uniform thickness and large areal extent, sills are likely the product of very fluid magmas. ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> Sills form only at shallow depths, whereas the pressure exerted by the weight of overlying rock layers is low. ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> One of the largest sills is the Palisades Sill ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> Columnar joints form when igneous rocks cool & develop shrinkage fractures that produce elongated pillarlike columns ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> Laccoliths form when magma is intruded between sedimentary layers in a near-surface environment ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> Batholiths –largest intrusive igneous bodies, occur as linear structures ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> evidence that supports that magma can move through solid rock are called inclusions called- xenoliths ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> magma originates in the upper mantle ·<span style="font-family: "Times New Roman"; font-size-adjust: none; font-size: 7pt; font-stretch: normal; font-style: normal; font-variant: normal; font-weight: normal; line-height: normal;"> mantle is solid, not molten rock
 * Intrusive Igneous Activity **
 * Nature of Plutons **
 * Dikes **
 * Sills and Laccoliths **
 * Batholiths **