How much of the Earth's surface is Sedimentary rocks?
rock or mineral fragments
What does Chemical weathering do?
dissolves rocks and liberates ions
clastic sedimintary rocks
formed from the eroded fragments of rocks and or fossils
examples of clastic rocks
claystones, siltstones, sandstones, conglomerates
precipitated sedimintary rocks
precipiated from waters supersaturated with dossolved ions or elements
examples of precipitated rocks
limestones, dolestones, salt, gypsum
are skeletal fragments of marine or land organisms that are found in sedimentary rocks laid down in a marine environment—especially limestone varieties
fine grained clastic rocks that contain a combination of silt and clay
thin layers of fine grained clastic rocks
fine grained clastic rocks made from thin layers that split apart easily
degree to which the angular corners and margins of the clasts have been worn away
degree to which the shape of a grain approaches a sphere. measure of shape
why is sphericity important?
it measures the amount of transportation
most stable mineral, most common, many colors, breaks like class, concoidal fracture
second most common sed. clasts, cleave along predermined flat surfaces
common ones are biotite and muscovite, silver to black brown flakes or cheets that are very thin
smaller grains filling in between larger clasts
degree to which the grains are held together after cementation
bioclastic carbonate formed in deep marine waters from the slow accumulation of calcite plates from microscopic planktonic
tiny planktonic algae that make up the composition of chalk
What happens to some of the magma after being subducted?
It returns to the continental side of the subduction zone
Pacific Ring of Fire
formed from subduction zone magma
two examples of island archipelagos
the Aleutians and the Hebrides
active mountain building portion of North America which experienced reactivated tectonic activity in the Pliocene-Holocene
what type of volcanes are the Cascade Volcanoes?
composite or strato-formed, explosive
When did Cascade volcanic activity begin?
5 million years ago
What are the two plates being subducted that create the magma for the Cascade volcanoes?
Juan de Fuca and Gorda plates-- underneath the North American Plate
How fast do the two plates move underneath the North American Plate?
2 to 3 inches per year
What are the two cascade volcanoes that have erupted in the last century?
Mt. Lassan (1914) and Mt. St. Helen (1980)