Geo Unit 1 quiz
Abundance of chemical elements in earths crust
Bulk of earths crust contain only eight chemical elements, Oxygen and silicon make up nearly 84% of availble atoms
Most abundaned elements in earths crust
oxygen and silicon
Extrusive Rocks ( or volcanic)
formed from volcanic action, molten magma cooled quickly on earths surface. Rocks consist of ver fine crystals, which are naked to human eye giving it an aphanitic strucutre.
- lighter ones are rich in silicon and aluminum ( silaic)
- darker ones are mafic
- most rocks have reltaviey uniform cooling
Intrusive rocks ( plutonic)
Formed from magma that has soldiifed deep inside the earth
- these rocks have cooled very slowly and have large crystals
- large crystal strucutre is phaneritic
- when rocks on surface erod, these plutonic rocks are pushed to the surface
- lighter rocks are sialic
-darker rocks are mafic
Igenous compisition ( felsic vs mafic vs intermediate)
🟡 Felsic
High silica content (≥ 65%)
Light-colored (white, pink, light gray)
Rich in quartz & feldspar
Low density, low melting point
Example: Granite, Rhyolite
🟠 Intermediate
Moderate silica content (55–65%)
Gray or salt-and-pepper appearance
Mix of felsic & mafic minerals
Example: Diorite, Andesite
⚫ Mafic
Low silica content (45–55%)
Dark-colored (black, dark gray, greenish)
Rich in magnesium & iron
High density, high melting point
Example: Basalt, Gabbro
Bowens reaction series
Describes order in which minerals crystallize from magma as it cools. Color of mineral indicates temp of magma.
- minerals form at different temps
-high temp minerals form first and are more unstable ( darker in color)more calcium rich
- At lower temp lighter colored minerals form and are more stable ( tey are more sodium rich)
Order: Olivine, pyroxene, amphibole, biotite mica, K felspar, muscoivte mica, Quartz
Ingenous structures (types)
Extrusive Structures: forms of volcanic rocks ( more detail alter)
Intrusive Strucutres: Bodies of plutonic rocks
Examples of Extrusive structures
- Lava plateau, Volcanic Cone
- Ropy Lava, Pillow Lava, Vesicular strucutre, Columnar jointing
Examples of intrusive strucutres
- Sheet intrustions ( sills, dikes)
-Lens shaped intrustions ( Laccolith)
-Large Bodies (Batholith, stock)
Theory of bowens reaction series
Discountinous VS Continous
discontinous - minerals that replace each other as cooling takes place
continous - minerals that crystallize over a range of tempettures
Coarse grained rocks
- individual minerals are large ( visible to human eye), they have a slow cooling ( intrusive)
- examples include granite and gabbro
Fine grained rocks
- indvidual minerals can only be seen with a microscope
- Fast cooling ( extrsuive)
- smooth
rock examples:
- Rhyolite, Basalt
Vesicular
contains gas bubbles (vesicles), giving it a spongey/bubbly texture
Glassy
No crystals, smooth like glass
- comes from extremely rapid cooling
Fragmental Pyrcoclastic
- Made up of fragments of volcanic material, that are ejected during volcainc eruptions
- contain angular fragments, or fine ash
lava Flows
Lava- molten rock material forced through
- A Vent ( this is when volcanic cone is formed: Which is just basic bitch volcanio, what you would expect)
- A fissure ( plateau lava - long narrow crack rather than cone , happens when plates pull crust apart, magma comes thru)
Volcanic Cones:
- Shield Volcano, broad , dome shaped - gentle slopes, formed by repeated flow of low viscosity lava ( which means runny and flows easy like melted syrup - creates gradual flow preventing pressure build up)
Eruption style: instead of sudden explosion, lava flows gently from vent, eruptioins can happen for a while
- Cinder cone volcanos , small, step sides, erupts explosviley but dont last long, made up from volcanic cinders that build up around vent
- Compisite volcanos, tall, steep sides, high viscosity lava ( thick like peanut butter, )this lava traps gas, leads to a buildup, when pressure becomes too much theres a violent explosion made up of alternationg layers of lava flow and ash)
Other extrusive structures
Columnar jointing:
- rock formation seen in volcanaci areas, as lava cools it shrinks, this causes the rock to crack into a hexagonal pattern , which form large vertical columns - the ones that look like steps
Joining -
more general term to descrive rocks breaking ( fractures) into other rock formations due to outside conditions
Volcanic Domes: steep dome shaped mounds, formed by the slow extrusion of thickkk ( high viscoisty) lava , since the lava is thick doesnst flow easy and piles up near the vent, creating dome like strucutre
Volcanicn crater: crater happens when a volcano explodes and the pressure from the eruption causes the ground to collapse ( awsome asf)
Strucutres of Lava
Pahoehoe Lava: smooth ropey, typically thinner lava ( low visocisty) these flows are fast moving and create intricate, rope like patterns as they cool, since lava is thin it can travel relativly far
AA Lava: Rough, jagged blocky surfaces, lava is a little thicker and moves a little slower. Has a chunky texture, sharp edges.
Pillow strucutre: rounded pillow like strucutre , forms when lava erupts underwater, or in ice. Cools quickly which forms round pillow like shapes. can build up on ocean forms and create new land forms ( sick asf)
Ash flows ( Nuree ardente): Fast moving , hot clouds of volcanic gas, ash and rock that are ejected during volcanic eruption, spread extremely fast super deadly,
these flows are a mixture of gases, ash, and debris moving incredibly fast and at high temperatures,
intrusive structures ( Sheet intrusions)
Sheet intrusions: sheet like bodies of magma that intrude between layers of existing rock then cool. Are plutonic since the are intrusive, two main types:
Dikes: verticla or steeply inclined sheet intrusions that cut across layers of rock. Form when magma forces itself into fractures in country rock, cooling in a near verticle orientation.
Sills: sheet intrusions parelle to country rock, typically horizontal or gently. inclined, magam goes into horizontal layers in the country rock, filling them then cooling into sheets, form large flat layers.
Intrusive structures ( Lens shaped intrustions)
Lens shaped intrustions: Happens when magma intrudes into surronding rock in lens like shape ( convex), intrustions are more horizontal or gentley inclined
Laccolith: intrusive lens shaped inclines, form when magma pushes up overlaying layer or rock, basically dome like strucutre , form convex ( outward curve)
Plutons
Plutons: More general term for intrusive rock strucutre
Batholith: Larges type of pluton, irregular, often form the core of mountain ranges,
Stock: Similar to batolotih, less than 100 square kilometers ( smaller batholiths basically
Xenioths
piece of rock that is embedded in another rock, a rock embedded in magma while the magma was cooling
Clasitic sediments
fragments or rocks that have been broken down due to weathering or erosion then cemented together. ( framgents or clasts cemented together)
Sedimentary rocks
rocks formed from the accumlation,cementation,and compaction of sediments
Chemical sediments
formed when dissolved minerals come out of solution either thru percpiptation ( inorganic) or biochemical ( organic)
Percpitiation: formed when minerals crystalize directly from water, due to evaporation or chemical changes, common from drying lakes or shallow seas
ex. Rock salt, from evaporated seawater
Gypsum, water evaporates in mineral solutions
Limestone: from dissolved calcium carbonate, in hot springs or caves
Biochemical: from living orginisims, shells, skeletons, or organic matter that later become sediments ( common in marine enviornment)
Lime stone: from shells and skeletons of marine animals
coal:compressed plant material (swampy enviornmetns(
Clastic sediments -> rocks they become
Clay sediments form shale ( tiniest particle , comapct and fine grain, need microshcope)
Slit sediments form siltstone ( 0.004 - 0.006 mm- visible under hand mirror)
Sand sediments form sandstone (less tahn 2mm but visible to naked eue)
pebbles (
cobbles
boulders
Chemical sediments ->> rocks they become
Dissolved salts -> rock salt or gypsum
perciptaed calcium carbonate -> limestone
Accumliated shells and marine fossils -> limestone
compressed plant matter ->coal
Sedimentary strucutres
- Stratification ( bedding) layes of sediments stacked over tiem
cross bedding - angled layers of sediments formed by forces like wind or water current
graded bedding - when bigger ( or coarser) sediments settle to the bottom first, then smaller or finer: larger grains at bottom, finer at top
foind in underwater landslides
ripple marks : symmertrical ripples formed by waves ( back and forht motion)
ayssmetircal ripples formed by river or wind currents ( one directional flow)
Mud cracks: form in drying mud, indicate the environemt goes between wet and dry ( ex, tidal flats)
Varves: thin alternating layers of sediment , form in lakes due to seasonal changes, kidna like tree rings record yearly cycle, and past climates
summer layer: light color coarser sediments
Winter layer: dark color finer sediments
Foliated vs non foliated
Foliated: minerals going into parrell layers or bands due to direct pressure, layered or banded apperance, adn can split along these layers ( mostly pressure, rocks being squished so hard crystals only grow in one way) - forms more from regional metamorphisism
Order ( increasing in metamorhphic grade)
-Slate
-Phylite
-Schist
-Gniess
Non foliated: lacks layered strucutre, because form under uniformed pressure , typicall forms from contact metamorphisism , more heat than pressure (baked)
marble: baked limestone
quartizte : baked sandstone
Metamorphic grade
Metamorphic grade refers to degree of metamorphimism rock has undergone, as these rocks change go from low degree to high degree
Metamorphic Grade Rock Types
Low Grade Slate, Phyllite
Medium Grade Schist, Marble
High Grade Gneiss, Quartzite
Contact vs regional
Regional - > Large scale’
-> plate tectonic forces
Ex omincea range ( land got added no to North America,
Collision thrusted up these rocks so you can find Marnie fossils on the rockies,
Collision and pressure that changes the area
Mainly pressure
( More complex than that tho)
Smaller scale metamorphosis - contact metamorphism
Heat changes sandstone from contact ( contact metamorphosis)
Ex if magma touches sandstone, the boundary ( contact area) becomes quartzite,
Small local formations of metapmorphisms
Mainly heat ( but more complex than that)
Metamorphic rocks to parent rocks
Slate ; parent rock shale
phylitee : parent rock slate ( sometimes shale)
Schist: parent rock phylite or shale
gneiss: parent rock granite or shale
marble: parent rock limestone
quarzitire: parent rock sandstone