Igneous Rocks form from Volcanic (surface)… …or Plutonic (subsurface) activity.

Metamorphic Rocks form from heat (Volcanic or Plutonic)… …or pressure and\or heat from Plate Tectonic ‘mountain making’.

SEDIMENTARY rocks, however, come from the weathering and re-working of igneous rocks, or precipitation of minerals… Clastic Rocks: Gravel Big, rounded pieces transported by water. CONGLOMERATESand Finer material, still coarse. SANDSTONE Clay The finest material… SHALE So where do these rocks form? (Environments of Deposition)

Environments of Deposition: where do these sediments (rocks) form? CONGLOMERATE is deposited in fast-moving water Mountain Streams… Wave-swept beaches

Sandstones: 3 major types… ARKOSE Sandstone Feldspar grains Arkose Sandstone represents ancient river channel and sand bar deposits from Granite bedrock. Environments of Deposition: where do these sediments (rocks) form? 25% Feldspar from eroded Granite. Quartz Sand is a clean sand often deposited as beaches. QUARTZ Sandstone

Graywacke Sandstone is associated with Stratovolcanoes, and therefore, with SUBDUCTION ZONES (colliding plates!). A lot of information from one rock! GRAYWACKEGraywacke Sand is a poorly- sorted deposit of volcanic sand from Stratovolcanoes. Subduction Zone Environments of Deposition: where do these sediments (rocks) form?

SHALE SHALE is clay deposited where water is NOT moving, as in lakes, deltas floodplains, swamps, quiet ocean bays… SHALE often represents environments of river floodplain and delta, lakebeds, or deep water ocean environment. Environments of Deposition: where do these sediments (rocks) form?

Limestone Carbonates (limestones), in general, form in shallow, tropical oceans. COQUINAS form in VERY shallow, near shore environment…the beach!). Carbonate Environments Precipitated rocks: Limestones

CHALK …Is another example of a rock made almost entirely of shells.

CHERT… …is microcrystalline QUARTZ. Most water-critters precipitate calcium carbonate… Some precipitate SILICA skeletons! Most cherts probably come from this organic process.

Some environments are RESTRICTED…water “leaves” only by evaporation. Sediments are precipitated by the evaporating water… These deposits are called EVAPORITES

Heat… and a restricted environment can cause… …many layers of HALITE (salt!) to accumulate in this fashion! GYPSUM is also a common evaporite!

In some areas, coastal areas are sinking. Periodic flooding of these sinking areas add more and more salt- saturated sea water. Heat, and the restricted environment, add layer after layer of Halite. GREAT thicknesses of Evaporite deposits may be formed. Ocean

The two requirements: Heat (warm climate) Restricted environment (water may not easily leave the “system”). Ocean Death Valley, and other parts of the American West Dead Sea… …and the Mediterranean at one time! Where?