New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

Geology notes

by: samantha Flavell

Geology notes GEO 100

samantha Flavell
SUNY Oswego
GPA 3.8

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

These are the notes for chapters 18 and 21
Physical Geology
Rachel Lee (P)
Class Notes
25 ?




Popular in Physical Geology

Popular in Geology

This 12 page Class Notes was uploaded by samantha Flavell on Friday April 1, 2016. The Class Notes belongs to GEO 100 at State University of New York at Oswego taught by Rachel Lee (P) in Fall 2015. Since its upload, it has received 13 views. For similar materials see Physical Geology in Geology at State University of New York at Oswego.

Similar to GEO 100 at SUNY Oswego


Reviews for Geology notes


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 04/01/16
Preferred Mineral Orientation *How does preferred mineral orientation develop? *Pressure solution­occurs in wet rocks at low T. *Minerals dissolve at compressed faces *Minerals grow where compression is less *Grains become shorter, parallel to compression. *Plastic deformation occurs at higher T. *Existing grains flatten by deforming internally *Shear Rotation and Flattening *Shear flattens grains in a manner similar to compression *Shear rotates grains into alignment Kinds of Metamorphic Foliation *Slaty Cleavage *Low Grade: alignment of clay minerals *Schistosity: *Medium­high grade: alignment of large micas *Compositional bonding(Gneissic bonding) *High grade: light bands of felsic minerals and dark bands of mafic minerals Intensity of Metamorphism *Rock type related to intensity Slate low grade Phyllite Schist Gneiss High grade Transition from shale to slate *Both rocks are extremely fine grained *Metamorphism and deformation cause clay minerals to recrystallize to micas and reorient into a strongly planar fabric, giving the product a near perfect ‘slaty cleavage.’ Transition from Shale to Phyllite *Micas continue to recrystallize and grow larger (yet not visible to the naked eye) *The texture of the rock becomes less perfectly planar. Phyllites in hand sample appear wavy  and shiny Transition from Phyllite to Schist *Recrystallization reactions make micas, quartz and feldspar large enough to see in hand sample. *The rock is still strongly foliated (from the dominance by micas) and commonly has  porphyroblasts of minerals like garnet and Al­Silicates. Transition from Schist to Gneiss *At higher P and T, micas begin to break down, forming minerals like garnet, feldspar and Al­ Silicates. *These reactions coupled with the mechanical difference between micas and quartz + feldspar  produce the banded appearance of gneiss *Gneiss and schists both have visible grains, but schists are dominated by micas and  gneiss has characteristic banding Formation of Foliation *Foliation more pronounced, crystals larger when metamorphism is more intense *Clays  Micas  Feldspar Migmatite *Many gneiss are called migmatites­ mixed rocks that combine metamorphic and igneous  (melted) components. (very high grade metamorphism mainly sedimentary protoliths) *The facing stone on funnel, cooper and hart hall are made of migmatite Sedimentary Protoliths Protolith Metamorphic equivalent Conglomerate (or breccia) Metaconglomerate Sandstone (all types) Quartzite Shale Slate…phyllite…schist…gneiss Grade: Low…medium…high Limestone Marble Sandstone v. Quartzite *Grains in clastic sedimentary rocks are cemented together and the cement is ordinarily  somewhat weak *When these rocks are metamorphosed, the first things to go is the cement *Grains are literally ‘fused’ together, make a densely interlocking frame work of grains Limestone v Marble *Why are most limestones dull and often dark in color whereas most marbles are bright white? *And where do those streaks in some types of marble come from? *The dark color of limestones comes partly from incorporated clastic material (clays) and  organic matter. *The metamorphic process boils out the volatile organics making a lighter color rock, and when  clays recrystallize during deformation, the new minerals formed take on folded, contorted and  streaked patterns Progressive Metamorphism *Note that basically the same textural changes occur if the protolith is a clay­rich sediment or a  fine­grained igneous rock. The specifics for the igneous protoliths, however, are different… Green Stones *At low grades, glass and many igneous minerals in extrusive (volcanic) rocks commonly  recrystallize to form fine grained green micas and amphiboles *Greenstones are green because the original igneous minerals have recrystallized forming green  metamorphic minerals Amphibolite *Greenstones taken to higher metamorphic grades are course grained rocks called amphibolite. *These can be massive, garnet­bearing rocks, as seen at Gore Mountain in the Adirondacks or…  ordinary looking gneisses. *Unlike gneisses with sedimentary protoliths, amphibolites are made up mainly of amphibole  (not mica) Metamorphic Grade *Prograde­ metamorphism via increasing T and P *Common in rocks that are buried in organic belts *Progressive changes *Recrystallization results in new mineral assemblages *Mineral changes release water *Retrograde­Metamophism via decreasing T and P *Common in rocks that are brought from depth by erosion or exhumation *Requires addition of H2O by hydrothermal fluids *Without added water, retrograde reactions cannot occur *Many metamorphic rocks preserve prograde conditions Metamorphic Facies *Mineral assemblages from a specific protolith at specific P and T conditions *Create rocks that are predictably similar *Named for a dominant mineral Index Minerals *Index Minerals indicate a specific P and T range *Useful for identifying P and T history *Index mineral maps *Define metamorphic zones *Boundaries are isograde Metamorphic Environments *Metamorphism occurs in different settings *Different settings yield to different effects via *Variation in the geothermal gradient *Changing gradients of different stresses *Variability in the nature of hydrothermal fluids *These characteristics are governed by plate tectonics *Types (and Settings) of metamorphism *Thermal: heating by plutonic intrusion *Burial: Increases in P and T by deep burial in a basin *Dynamic: Shearing in a fault zone *Regional: P and T alteration due to orogenesis *Hydrothermal: Alteration by hot water leaching *Subduction: High P, low T altercation *Shock: Extreme high P attending a bolide impact Thermal (Contact) Metamorphism *Due to heat from magma invading host rock *Creates zoned bonds or alteration in host rock *Called a contact or metamorphic aureole *The aureole surrounds the plutonic intrusion *Zoned from high (near pluton) to low grade (far from pluton) *Grades of alteration form aureoles around the pluton *Bands range from highly altered to increased heating *The width of each aureole zone is due to: *The size of the plutonic intrusion *The degree of metasomatism *The dominant rock is hornfels Burial Metamorphism *As sediments are buried in a sedimentary basin *P increases because of the weight of the overburden *T increases because of the geothermal gradient *Requires burial below diagenetic effects *This is ~8­15km depending on the geothermal gradient Dynamic Metamorphism *Breakage of rock by shearing at a fault zone *Fault location determines type of alteration Shallow crust­upper 10­15km *Rocks behave in a brittle fashion *Mineral grains crush forming fault breccia Deeper crust­Below 10­15km *Rocks are ductile *Minerals smear like taffy to form mylonite Regional Metamorphism *Tectonic collisions deform huge “mobile belts” *Directed compression thickens mountains *Rocks caught up in a mountain building are *Heated via the geothermal gradient and plutonic intrusions *Squeezed and heated by deep burial *Smashed and smeared by differential stresses *Regional metamorphism creates foliated rocks *This type of metamorphism is, by far, the most important in terms of the amount of rock altered *Collisional belts are often: *Thousands of km long *Hundreds of km wide Hydrothermal Metamorphism *Alteration by hot, chemically aggressive water *A dominant process near mid­ocean ridge magma *Cold ocean water seeps into fractured crust *Heated by magma, this water then reacts with mafic rock *The hot water rises and is ejected via black smokers Subduction Metamorphism *Subduction creates the unique blue schist facies *Trenches and accretionary prisms have: *A low geothermal gradient (low T, high P) *These conditions favor glaucophane, a blue amphibole mineral Shock Metamorphism *Rarely, Earth is struck by a comet or asteroid *Impacts generate a compressional wave *Extremely high pressure *Heat that vaporizes or melts larger masses of rock *These conditions generate high pressure minerals Exhumation *How do metamorphic rocks return to the surface? *Exhumation is due to uplift, collapse and erosion Finding Metamorphics *Large regions of ancient high­grade rocks­ called shields­ are exposed in continental interiors *Shields are eroded remnants of organic belts *Shield rocks form the basement under sedimentary cover Geological Structures *Wherever you see sedimentary rocks that aren’t lying horizontally these rocks have been  DEFORMED in some large­scale process *It’s important to try to imagine the scale of the entire structure to which a single area or outcrop belongs Deformation *As a result of plate tectonics, the crust is constantly under stress *Rocks respond to stress by deforming *Deformation may be brittle, in which rocks will tend to break, or ductile in which rocks will  tend to flow or bend ­Temperature ­Pressure ­Deformation Rate ­Composition *Displacement: change in location *Rotation: Change in Orientation *Distortion: Change in Shape Types of Stress *There are three principle types of stress 1) Compressive 2) Tensional 3) Shear **Pressure isn’t the same as stress Traces of Stress in Rocks *By measuring objects of known undeformed dimensions, we can estimate the nature and  magnitude of deformation. Brittle Deformation *Brittle deformation breaks rocks *When rock breaks and no movement takes place then it is a fracture *When rock on the sides of the fracture move then it is a fault Describing Orientation of Geologic Features with Strike and Dip **A planar structures orientation can be specified by strike and dip STRIKE: Angle between an imaginary horizontal line on the structure and the direction of true  north. DIP: Angle of the structures slope Fault Orientation *We classify faults based on direction of movement of individual blocks, with reference the  Earth’s surface (horizontal) *On a dipping fault, the blocks are classified as the  *Hanging­wall block (above the fault) AND *Footwall block (Below the fault) *Standing in a tunnel excavated along the fault *Your head, is near the hanging­wall block *you are standing on the footwall block Fault Classification *Fault geometry varies­vertical, horizontal, dipping *The relative motion of the offset block varies *Dip slip: blocks move parallel to dip of the fault *Strike­slip: blocks move parallel to fault plane strike *Oblique slip: components of both dip slip and strike slip Dip­Slip Faults *Sliding is parallel to the dip of the fault *Blocks move up or down the slope of the fault *The two kinds of dip­slip fault depend on relative motion *Reverse fault: the hanging wall moves up the fault slope ­Thrust fault (a special type of reverse fault) *Normal fault: the hanging wall moves down the fault slope Normal Faults *The hanging wall moves down relative to the footwall Reverse and Thrust Faults *The hanging wall moves up relative to the footwall *Reverse faults: Fault is steeper than 35 degrees *Thrust faults: fault deep is less than 35 degrees *Accommodate crustal shortening (compression) Thrust Faults *Place older rocks on top of younger rocks *Common at the leading edge of orgenic deformation *Can transport thrust sheets hundreds of kilometers *Act to shorten and thicken mountain belts Strike­Slip Faults *Fault motion is parallel to the strike of the fault *Usually vertical, no hanging wall­footwall blocks *Classified by the relative sense of motion *Right lateral: opposite blocks move to observer’s right *Left lateral: opposite blocks move to observers left *Large strike­slip faults may slice the entire crust Faults *Faults may offset large blocks of Earth *The amount of offset is a measure called displacement *The San Andres displacement of hundreds of Km Fault Recognition *Continuous features are displaced across a fault  *Faults may juxtapose different kinds of rock *Friction may bend rocks near the fault into drag folds *Brittle faulting results in shattered and crushed rock *Fault breccia consists of rock fragments along a fault *Fault gouge is made of polarized, powdered rock *Scarps are visible when faults intersect the surface *Fault zones with breccia and gouge preferentially erode *Ductile faults create plastically deformed rocks *Rocks don’t break, instead they are intensely sheared *Rocks from ductile shear zones are called mylonites *Mylonites typify detachment faults in collisional orogens Fault Systems *Faults commonly occur in groups called fault systems *Due to regional stresses that create many similar faults *May diverge from a common horizontal detachment fault


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"

Anthony Lee UC Santa Barbara

"I bought an awesome study guide, which helped me get an A in my Math 34B class this quarter!"

Steve Martinelli UC Los Angeles

"There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."

Parker Thompson 500 Startups

"It's a great way for students to improve their educational experience and it seemed like a product that everybody wants, so all the people participating are winning."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.