Deep marine deposits—fines settle out far from land.Skeletons of planktonic organisms make chalk or chert.Fine silt and clay lithifies into shale.Lahars with some recent examples-Lahars is one of many volcanic hazards -Lahars—mudflows result when water moves ash.oLike concrete, this material is more dense than water. oIt can carry away everything (people, houses, bridges).
Gneiss and other major metamorphic rock types: evolution and protolithsMetamorphic rock—solid-state alteration of a protolith. -Meta = change.-Morphe = form.-Protoliths are preexisting rocks.-Metamorphism can alter any protolith. What is a metaphoric rock?-Metamorphism changes mineralogy.oRed shale—quartz, clay, and iron oxide.oGneiss—quartz, feldspar, biotite, and garnet.-Metamorphism changes texture.oUnique texture—intergrown and interlocking grains-Metamorphism often creates foliation.oA texture defined by:Alignment of platy minerals (i.e., micas) Creation of alternating light/dark bands-Metamorphic rocks have been modified by heat, pressure, and chemical processes, usually while buried deep below Earth's surface. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks.Types of metamorphic rocks
-Foliated metamorphic rocks such as gneiss, phyllite, schist, and slate have a layered or banded appearance that is produced by exposure to heat and directed pressure-Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance. Pictures and brief descriptions of some common types of metamorphic rocks are shown on this page.Gneiss-