Exam 3 Flashcards
How is the geologic time scale broken up into [Earth’s Calendar]
Eons(greatest Expanse of time) Eras Periods Epochs (smallest expanse of time)
What are the two major divisions in the geologic time scale?
———–present——- Phanerozoic Eon (eon of visible life) (15% of earth’s history) ———-543 million years ago——- precambrian (85% of earths history) ———4.6 billion years ago——-
What are the tree eras of Phanerozoic Eon
Cenozoic Era (recent life) [includes the present], age of mammals (starts 65m.y.a w/ K/T extinction) Mezozoic Era “Middle life” [Age of dinos] (starts 252 m.y.a. w/ permian extinction) Paleozoic Era “Ancient life”(begins 543m.y.a.) [explosion of life]
Moon was closer to earth when?
early precambrian (EON)
The moon formed in the
The Precambrian (Eon)
The most efficient organism that dominated in early paleozoic Era
Trilobite 500 different genera
Life on land is
recent in geologic sense
Greatest mass extinction
it was the Permian Extinction (almost complete annihilation) 95% of life were extinct
group of animals that dominated earth for 200 million years
Dinosaurs
What extinction event wiped out the dinosaurs?
K/T extinction event 70% of all life died
How many mass extinction events are in the phanerozoic (Eon)
five (sixth is going on today by humans)
two largest mass extinction events in Phanerozoic
K/T extinction Permian extinction
Two people who found evidence for the cause of K/T extinction?
Walter (son) and Luis Alverez They Found a thin layer of clay
What did they find the clay contained?
- Iridium (high concentration) [orginal found by the Alvers] 2. Micro-tektites (Small glass spheres) 3. Shocked- Quartz 4.Soot (from global wildfires)
Where is the impact crater for K/T extinction
Mexico’s Yucatan Peninsula
Scenario of events from K/T impact meteor
Tsunami Heat Wave (forest bursting in flames) Blackout (dust and smoke blocked out the sun’s energy) Deep Freeze (slowly filtered out) Acid Rain and global warming (this is prolonged)
opposing hypothesis for the K/T extinction
The massive eruption of lava occurred in India Deccan flood basalt province
Deccan flood basalt province resulted in
- SO2 emissions- contributed to cooling and acid rain 2. CO2- increase in the green house effect 3. CI - depletes the world’s ozone layer
Antipodal Hypothesis is
The chicxulub impact may have generated a shock wave that travel through the earth and cracked the lithosphere and produced outpouring of basalt lava.
What is the prevailing idea for the Permian Extinction?
Plate tectonics and Siberian Flood basalts (occured roughly 252 MYA) (making the climate change)
Types of bodies that are possible to hit earth
Comets Stony meteorites Iron Meterorites
What are in complex craters?
central uplift impact melt (between uplift and rim) Ejecta blanket (has tektites, broken rock, and shocked quartz)
Simple crater contain
May not have impact melt, smaller in diameter no central uplift has ejecta blanket
events for impact crater formation
Meteorite impact then compressional wave with heat blow material out central upwave created by rebound leaves a fractured blanket
Meteor Crater, Arizona
youngest and best preserve crater (about 50000 years old) Recognized as impact crater by Gene Shoemaker
Tunguska Event (1908)
meteorite impact in Russia First expedition to check it out was in 1921 (FAILED) Second expedition was in 1927 No crater found b/c it was a stony Meteorite
program to catalog objects with orbits that cross earth’s orbit
Spacewatch Program (Still in operation @ Uof A)
What did it take to get the Spacewatch program to be funded?
The Shoemaker-levy Comet crashing into Jupiter
WHat are they two belts of comets
Oort Cloud Kuiper Belt (Both are beyond neptune)
Surface of Mercury Venus Saturn’s icy moon (enceladus) Mars Moon
Mercury-very heavy with impact craters Venus-numerous impact crater Enceladus-Dynamic body (resurfaces its body) Frozen water Mars-it has craters Moon- lots of craters
What is the magma chamber
reservoir of molten rock beneath volcano(feeds the volcanic eruption)
what happens when magma cools in the magma chamber or on the surface?
it produces into intrusive igneous rock (crystallizes) or feeds an eruption where it cools on surface and becomes extrusive igneous rock
Intrusive igneous rock
cools inside the magma chamber (large crystals) [more time to cool] course-grained crystalline structure (magma)
Extrusive igneous rock
cools more rapidly and produces a fine grain igneous rock (lava)
Differenced between magma and lava
magma is interior of earth lava is not lava is degassed rock (less pressure) soda example
Glassy texture
rock with no crystals from rapid cooling or quenching of lava ex. obsidian (entering water)
Vesicular texture is
rock with open spaces (gas bubbles that are trapped within the rock) example of this is pumice
Pyroclastic texture is
texture that is fragmented by explosive eruptions (associated with more explosive eruption)
Extrusive rock: Basalt Andesite Rhyolite
Dark (less Silica) lighter (more silica) light (has the most silica)
What controls the nature of the eruption
Viscosity amount of dissolved gases
What is viscosity and what are its controls
ability to resist flow (think of honey example) A) temperature (hotter the lower the viscosity and vice-versa) B)Magma composition- the higher the the silica the higher viscosity
Describing the nature of eruption amount of dissolved gases
this provides the driving force of the eruption (think of soda analogy) mgma contains dissolved gases b/c it is under pressure
what determines whether the eruption is explosive or not
the viscosity (the higher the viscosity the bigger the explosion) (analogy of spaghetti sauce blowing up)
WHat are the products of eruptions?
- Lava flows (nonexplosive) 2. Volcanic gases (drives the eruption) 3. Pyroclastic material (more explosive)
Lava flows are and what are the two types? Which one has higher viscosity?
low viscosity Pahoehoe- fluid lava with a smooth surface A’a - thicker lava flow with a rough spiny surface A’a has a higher viscosity
How are lava tubes created
as lava begins to cool along the sides a hot rind is created that insulates the lava flow (it allows the lava to continue down the slope once the eruption ceases the basalt lava will drain out leaving an open tube
What happens when lava hits the water?
Pillow basalts are formed
What are the main volcanic gases
H2O CO2-contributes to global warming SO2-contributes to global cooling
What is Tephra?
Pyroclastic material (it is the eruption column) separated into three sizes 1. ash less than 2mm 2. Lapilli 3. Blocks and bombs greater than 64mm All are liquid when they erupt except block
what is a block
they were never liquid but same size of a bomb
How are volcanoes distributed (how do we have volcanos)
- Spreading center volcanism 2.Subduction Zone volcanism 3. Intraplate Volcanism
What is created in spreading center volcanism?
basalt magma
The pacific rim were volcanoes are active is called
the ring of fire
what is the average composition that can erupt in a subduction zone volcano is
andesite (dangerous b/c very explosive)
Intraplate volcanism
the type of melt generated is basalt
Features of a generic volcano
fed by magma chamber summit crater is on the top central vent connects magma chamber and summit crater
What are parasitic cones and fuma role
they volcanoes erupting off the side of a volcano fumarole are where gases erupt on the side (stinky)
WHat are the three main volcano types
Shield volcano-low profile (calm gentle eruptions) 100% basalt Scoria volcano- very steep slopes w/ large summit crater (smallest of the three) Composed of basaltic tephra more explosive Stratovolcano-small summit crater (most explosive) Avg composition is andesite
Shield volcano
-low profile (calm gentle eruptions) 100% basalt lava flows
Scoria volcano
very steep slopes w/ large summit crater (smallest of the three) Composed of basaltic tephra more explosive
Stratovolcano
small summit crater (most explosive) Avg composition is andesite ( has both tephra and lava flows)
Example of shield volcanos
Mauna Loa Hawaii (largest volcano) [Tallest volcano is Mauna Kea] (tallest mountain)
Example of Scoria Cone
Paricutin, Mexico (1943-52) the eruption covered the entire village
Stratovolcano is associated with
subduction zones
What are Plinian eruptions?
they are the most explosive type of eruption ex. a “plinian event”
Important volcanic features (mostly associated with stratovolcanoes)
- lava domes 2. Calderas
What are lava domes
bulbous mass of viscous material rising from the throat of the volcano (they mark the end of plinian eruptions)
What are calderas?
large circular depressions produced when weight of the volcano causes it to collapse into its own magma chamber (associated with the largest plinian eruptions)
example of a calderas
Crater lake Oregon (formed from Mt. Mazama)
WIzard Island is
a small volcano formed on crater lake
WHat happened at Lake Nyos, Cameroon
12000 people died b/c landslide occurred at the lake and all the CO2 bubbled out as the water rose and suffocated everything
What are catastrophic phenomenons associated with planian eruptions
- pyroclastic Falls 2. Pyroclastic flows 3. Lahars (volcanic mudflows)
What are pyroclastic falls?
Volcanic material rising high in the sky and eventually falling down ex. wet ash accumulating on roofs causing it to collapse ex. respiratory problems affects airliners
Volcano that buried Pompeii and Herculaneum
Mt. Vesuvius killed about 3000 people ash cover Pompeii and pyroclastic flow covered Herculaneum
WHat are pyroclastic flows?
fluidized mixture of solid to semi-solid fragments and hot that contains toxic gases (this flows down the flanks of a volcano and towards valleys)
WHo are Maurice and Katia Kraft?
Volcanologists that photographed eruptions Died from a pyroclastic flow
Mt. Pelee in Martinique
It erupted in 1901 and a pyroclastic flow destroyed the Village St. Pierre
WHat was unique about the lava dome at mt. Pelee?
it grew at 50 ft per day (500 ft thick) it collapsed because it was too large
What are Lahars?
Volcanic mudflows (pyroclastic material mixed with water)
WHere does the water come from for pyroclastic flows?
- rainfall 2. ice and snow melt 3.disruption of crater lakes
Example of a deadly Lahar?
Nevado del ruiz Columbia (people thought they could get an early warning if a lahar were occur)
Mt. Rainier’s previous Lahars are?
- Oseola Lahar 5700 years ago 2. Elecrton Lahar occurred 500 years ago (major concern b/c there are about 300000 people)
What are super-Eruptions?
The eruption of voluminous pyroclastic sheet flows from giant resurgent calderas (sheet flow as in covering up and filling up the valley)
What are the most recent super-eruptions?
Taupo, New Zealand(26000 years ago) Toba, Indonesia(74000 years ago)
Areas in the U.S. with super-eruptions (less than 1 million years ago)
1.YellowStone National Park (caldera of 85 KM) 2 Long Valley, California (USGS vs locals incident)
where doe the pyroclastic material come out from for super eruptions?
large fracture around the ring of the caldera
the volume amount of pyroclastic material
is related to how explosive the eruption is.
USGS new alert system
it is for monitoring future eruptions and keeps the public informed through four levels Helped saved lives on Mt. Pinatubo
THe Pu’u O’o eruption is an example of what kind of eruption?
calm eruption with the outflowing of basaltic lava
What is the Hawaiian hotspot track?
A chain of hawaiian islands that extends north west (age of all the islands and volcanoes get older as you go north west)
WHat has been creating the hawaiian islands?
a mantle plume and a plate with constant motion (mantle plume doesn’t move but as the plate moves a new volcano forms)
How many shield volcanoes are on the big island of Hawaii?
5
name the caldera on the kilauea shield volcano
Halemaumau
WHat are the two types of eruptions in Hawaii
- summit crater eruptions “fire fountaining” 2. Fissure eruptions “curtain of fire”
The cascad Mountains are strato volcanos because of
subduction zone of the Juan de Fuca plate
Who was Harry Truman and David Johnston
Harry Truman- owned the Mt St Helens lodge (didn’t want to leave and died at the eruption)
David Johnston- died while he was on watch (body was never found)
Series of events for the climatic eruption of mt st Helens
- 5.0 M eathquake
- Earthquake triggered a giant lanslide
- then producing a super heated water directly North (lateral blast)
- the removal of the material released pressure off the magma and produced a plinian eruption (rising form summit area)
