Format of exam: 36 multiple choice questions. 5 images
Terms to know: vesicular, aphanitic, phaneritic, fragmental, breccia, pyroclastic, felsic, intermediate, mafic, ultramafic, lopolith, laccolith, stock, sill, dike, batholith, neck, fractional crystallization, partial melting, assimilation, pahoehoe, aa, block flow, lahar, eruption column, fire fountain, pyroclastic flow.
You should know the crystallization sequence described by Bowen (Bowen's reaction series)--this is given on page 96 of your lab book and is also on the "in-class exercises" web page of this site. Which minerals crystallize first; which crystallize last?
You should understand how melting occurs: pressure relief melting (at mid-ocean ridges and hot spots) always produces basaltic magma; melting via addition of water lowers the solidus temperature (at subduction zones) and generally produces intermediate composition melts. Heat transfer can only melt rocks that are more silica rich than the magma from which the heat is being transferred and results in bimodal volcanism at continental hot spots.
You should know the different volcano types, what they look like, and what they are made of: shield volcanoes (basalt); stratovolcanoes/composite volcanoes (mainly intermediate composition lavas and ash--so andesitic); cinder cones (scoria), domes (mainly intermediate and felsic lava-so andesite and rhyolite). You should know that a pillow structure indicates that the lava cooled under water.
You should be able to come up with the name for any of
the igneous rocks in the chart below. Understand the difference between
crystalline rocks and noncrystalline (vesicular, fragmental, glassy) rocks.
Make sure you understand the difference between a MINERAL and a ROCK!!!
Classification of igneous rocks
|Crystalline-means||made from many||individual mineral||grains that grew in||a melt|
|Minerals you'd||expect to find in||this composition||crystalline rock||.|
| quartz, potassium
|Other rocks - such||as those made from||glass or fragments||of rocks or ash||.|
holes than rock)
also called vesicular
Extra stuff: A basalt containing holes (more rock
than holes) is called a vesicular basalt.
You should be able to distinguish between mechanical weathering (which breaks material into smaller fragments without making any chemical changes) from chemical weathering (which alters the chemistry of the material)
Mechanical weathering we discussed includes: abrasion, salt cracking, frost action/wedging, activity by organisms, pressure release/exfoliation, thermal expansion and contraction.
Chemical weathering we discussed includes: hydrolysis/hydration, oxidation, dissolution -- you should be able to recognize each when written as a chemical reaction by looking at the products. Dissolution will not have any solids among the products. Oxidation will have at least one product that is a solid containing Fe and O in its formula, and Hydrolysis/hydration will contain at least one solid mineral in its products that contains an OH in its formula.
You should know what the products of chemical weathering
if the rock contains minerals that have iron (such as the pyroxene or amphibole or olivine in a basalt or gabbro), then you will get hematite (an iron oxide)
if the rock contains a mineral with aluminum and silicon, such as feldspar (which is pretty much any igneous rock), then you will get a clay mineral
if the rock contains quartz (such as a granite, but definitely NOT a basalt), then you will get quartz grains
Those are basically the three solids that you expect. You will also get ions/atoms in solution in all cases.
some of the descriptions of rocks may say a "clastic rock which feels smooth when rubbed between fingergs"-- you should think shale - see below in chart. Be able to distinguish between clay and silt sized sediments. Understand that cross-bedding indicated wind or stream flow direction. Understand what happens when a clastic sediment becomes mature (rounding and sorting) and that this involves transport by wind and/or water, but not ice. You should understand the criteria by which each of the rock types are classified (grain size for clastic, for example).
Classification for clastic/detrital sedimentary rocks (classified on the basis of grain size)
|Grain size||Name of Rock|
|Gravel (includes boulders, cobbles, pebbles, granules|| if grains are angular: breccia
if grains are rounded: conglomerate
|Sand - will feel gritty when rubbed between fingers|| sandstone
- if contains more than 90% quartz: quartz sandstone
- if contains more than 25% feldspar: arkose
- if poorly sorted with a lot of mud: graaywacke
|Mud - will feel smooth or powerdery when rubbed between
- includes silt (feels gritty against teeth)
- includes clay (feels smooth against teeth)
|if breaks along flat surfaces (fissile): shale|
Classification of chemical sedimentary rocks (classified on the basis of mineralogy)
|made from silica (SiO2)||made from calcite (CaCO3)
all will react with HCl
|made from other minerals|
|chert - microcrystalline quartz
(hard and tends to show conchoidal fracture)
diatomite - made from diatom shells (easily confused with chalk)
|limestone - generic name
oolitic limestone - spherical grains like tiny beads
chalk - made from shells of tiny plankton
coquina - made from visible shells or shell fragments
travertine - forms in caves and often has a banded appearance
|dolostone - made from dolomite
rock salt - made from halite
rock gypsum - made from gypsum
And then there is coal - peat to lignite to bituminous coal.