Untitled Flashcards Set

GEOLOGY

PETROLOGY- deals with the mode of formation, structure, texture, composition, occurrence, and types of rocks.

GEO- EARTH

LOGOS – DISCOURSE/STUDY GEOLOGY SI CONCERNED WITH:

-Earth and rocks of which it is composed.

-processes by which they are formed during geological time.

-modeling of the earth’s surface in the past and present day.

-the cycle of geology encompasses all major processes, which must be cyclic, or they would grind into an inevitable halt.

-Land- erosion and land destruction

-Sea- depletion and formation of new sediments

-Underground- creation and deformation of rocks.

CORE BRANCHES:

PHYSICAL GEOLOGY- examines the materials COMPOSING earth, seeks to understand the many processes that operate on and beneath its surface.

HISTORICAL GEOLOGY (STRATIGRAPHY)-

seeks to understand the origin of earth and its development through its 4.6-billion-year history.

BRANCHES:

MINERALOGY- deals with the mode of formation, composition, occurrences, types, associations, properties, and uses of minerals.

RULES:

NIHDO (

Naturally occurring, Inorganic, Homogeneous solid, Definite chemical composition, Ordered crystalline structure)

STRUCTURAL GEOLOGY- deals with the mode of formation, causes and classification of geological structures such as folds, faults, joints, and unconformities of rocks.

SIGNIFICANCE:

-provides a systematic study of the structure and properties of construction materials and their occurrence.

-provides knowledge about the site used in construction of buildings, dams, tunnels, tanks, reservoirs, highways, and bridges.

-helps to identify areas susceptible to failures due to geological hazards such as an earthquake, landslide, weathering effects, etc.

ENGINEERING GEOLOGY:

-deals with the application of geologic knowledge in the field of civil engineering, for execution of safe, stable and economic constructions like dams, bridges, and tunnels.

-studies may be performed during planning, environmental impact analysis, structural engineering design, construction, post- construction, and forensic phases of the project.

MAIN CONCERNS:

-soil/rock deformability pattern

-stability

GEOTECHNICAL ISSUE:

-road subsidence

-road damage

-bridge wash out

-liquefaction

-landslide

MYSTERY: LEANING TOWER OF PISA, ITALY

-soft ground and settlement

-weak ground and potential failure

-unstable slopes and potential sliding

-severe river or coastal erosion

-potential earthquake hazard

-potential volcanic hazard

PLATE TECTONICS

-deals with the dynamics of lithosphere.

-attributes the movement of massive sections of the earth’s outer layers to creating earthquake, mountains, and volcanoes.

-combined the theory of continental drift with the theory of seafloor spreading.

-the outermost portion of the earth is composed of thin rigid plates that move horizontally with respect to one another.

-plates interact with each other along their edges (plate boundaries).

-plate boundaries have a high degree of tectonic activity (mountain building, earthquakes, active volcanoes).

OBJECTIVES:

-describe how plate tectonics started with continental drifts.

-describe the physical and chemical layers of the earth and how they affect plate movement.

-explain and identify the three layers of plate boundaries.

MAPPING OF THE OCEAN FLOORS

-in 1947, researchers started using SONAR to map a region in the middle of Atlantic Ocean.

-by 1953, Marie Tharp and Bruce Heezen had created the first detailed map of the ocean floor that revealed the Mid-Atlantic Ridge.

CONTINENTAL DRIFTS HYPOTHESIS

ALFRED WEGENER

-German scientist who specialized in meteorology and climatology.

-first to advance the idea of mobile continents.

-identified several lines of evidence to support the idea that the continental masses drifted across the earth.

-proposed that all continents formed one large land mass that he calls Pangea.

-despite the evidences to prove his theory, he could not answer one question: “how were the continents moving?”

-died in 1930 on an expedition in Greenland.

-however in the 1950s, evidence started to trickle in that made continental drift a more viable idea.

-what’s the missing mechanism?

EARLY EVIDENCE

FRANCIS BACON (1620)

-noticed the similarities in the coastlines of south America and Africa on the first world maps.

ANTONIO SNIDER-PELLEGRINI (1858)

-did preliminary work on continental separation and matching fossils.

CONTINENTAL DRIFT HYPOTHESIS: EVIDENCES

CONTINENTAL FIT EVIDENCE- coastlines of some continents fit together like pieces of jigsaw puzzle.

GEOLOGICAL/BIOLOGICAL EVIDENCE- similar

rocks, mountains, fossils, and glacial formations across oceans.

CLIMACTIC EVIDENCE -similar glacial deposits are found in antarctica, south America, and India, now thousands of kilometers apart.

SEAFLOOR SPREADING HYPOTHESIS

HARRY HESS

LAYERS OF EARTH

-essential to understand the details of plate tectonics.

-different layers based on chemical composition and physical characteristics.

CHEMICAL LAYERS OF THE EARTH:

Factors for creating three distinct chemical layers:

-temperature

-pressure

CHEMICAL LAYERS

-gradual addition of new oceanic crust in the ocean floor through volcanic activity while moving the older rocks away from the mid- oceanic ridge.

SEAFLOOR SPREADING THEORY: EVIDENCES

-basalt oceanic crust and overlying sediment become progressively younger as the mid- ocean ridge is approached, and the sediment cover is thinner near the ridge.

PALEOMAGNETISM-magnetic surveys

CRUST

-outermost and thinnest chemical layer.

-landscape on which we live in: rocks, soil, and seabed.

-rocky silicate material with some aluminum and trace of amounts of all the naturally occurring elements.

-the base of the crust is characterized by a large increase in seismic velocity.

conducted near the mid-ocean ridge showed elongated pattern of normal and reverse polarity of the ocean floor in bands paralleling the rift and symmetrically distributed as mirror images on either side of it.

MID-OCEAN RIDGE

-50,000-mile chain of volcanic mountains in the middle of the ocean.

-a rift valley is a deep crack that runs through them.

-seafloor spreading happens here.

MID-ATLANTIC RIDGE

-an underwater mountain range that spanned the length of Atlantic Ocean with rock chemistry and dimensions unlike the mountain found in the continents.

MOHOROVICIC DISCONTINUITY

-discovered by Adrija Mohorovicic in 1909 after studying earthquake wave paths in Croatia.

-underneath the oceans, moho is found roughly 5km below the ocean floor.

-under the continents, it is located about 30 to 40km below the surface.

TYPES:

CONTINENTAL CRUST

-underlies the continents.

-has a relatively low density and composition similar to granite.

-thickness ranges from 30 to 70km.

OCEANIC CRUST                                            PHYSICAL LAYERS OF THE EARTH

MANTLE

-underlies the ocean basins.

-relatively high density, especially when cold and old.

-compositions similar to basalt.

-thickness ranges from 6 to 12km.

-the earth can be broken down into five distinct physical layers based on how each layer responds to stress.

LITHOSPHERE

-outermost layer of the earth ~100km thick and is defined by its mechanical properties.

-rigid layer that includes the brittle upper

-sits below the crust and above the core.

-largest chemical layer by volume, extending from the base of the crust to a depth of about 2900km.

-composed of silicates with large amount of iron and magnesium.

GUTENBERG DISCONTINUITY

-the base of the mantle, at the boundary with the outer core.

-named after Beno Gutenberg.

-primary seismic waves (P waves) slow down while secondary seismic waves (S waves) vanish completely at this depth.

PERIDOTITE XENOLITH WITH OLIVINE (GREEN)

-data comes from seismic waves analysis, and by studying ophiolite and xenoliths.

-the sample is chemically weathered by hydrolysis and oxidation into iddingsite.

-the more altered side of the rock has been exposed to the environment longer.

CORE

-has both liquid and solid layers.

-consists mostly of iron, nickel, and possibly some oxygen.

-discovered in 1906 by scientist looking for seismic data.

-magnetic iron and nickel in the core that is thought to be responsible for earth’s magnetic field.

portion of the mantle and the crust.

-contains oceanic and continental crust.

-coolest layer in earth in terms of temperature.

ASTHENOSPHERE

-layer below the lithosphere.

-moves and flows due to convection currents

created by heat coming from the earth’s core.

-relatively broken unlike the lithosphere which consists of multiple plates.

MESOSPHERE

-sometimes knows as the lower mantle.

-more rigid and immobile then the asthenosphere.

-located at a depth of 410 to 660km below the

earth’s surface.

-subjected to very high pressures and temperatures.

OUTER CORE

-only entirely liquid layer within the earth.

-starts at a depth of 2890km and extends to 5150km, making it about 2300km thick.

-important in maintaining a breathable atmosphere and other environmental conditions favorable of life.

INNER CORE

-the solid inner core is about 1220km thick, and the outer is about 2300km thick.

INGE LEHMANN

-analyzed seismic data and was the first to prove a solid inner core existed within a liquid outer core.

PLATE TECTONIC BOUNDARIES

PLATE TECTONIC BOUNDARIES: TYPES

DIVERGENT PLATE BOUNDARIES

-as plates move apart, new oceanic lithosphere forms continually along the divergent boundary.

-sometimes called constructive boundaries.

TYPES:

CONTINENTAL RIFTING

-in very thick continental plates, strong convection currents develop that push mantle material up against the overlying plate.

-tensional forces created by this convective upwelling begin to pull the weakened plate apart.

-normal faults are deep cracks that develop as the plate stretches and becomes thinner.

-eventually, plate sections drop into deep depressions know as rift valleys.

-rift valleys often contain grabens and horsts.

-rifts have earthquakes and may also exhibit volcanism.

-rift-zone magma is created by decompression melting.

TWO TYPES OF RIFTS:

NARROW RIFTS

-characterized by a high density of highly active divergent boundaries.

BROAD RIFTS

-have numerous fault zones, but they are distributed over wide areas of deformation.

MID-OCEAN RIDGES

-the only place that create new oceanic lithosphere.

-the change of asthenosphere material into new lithosphere is due to decompression melting in the rift zone.

CONVERGENT PLATE BOUNDARIES

-places where two or more plates move towards each other.

-also called destructive boundaries.

MOVEMENT TYPES:

SUBDUCTION

-occurs when a dense oceanic plate meets a more buoyant plate.

-as an oceanic plate descends, it pulls the ocean floor down into a trench.

-plate edge bends down and slips into the mantle, then the leading edge sinks downward like an anchor rope.

SUBDUCTION ZONES

-known for having the largest earthquake and tsunamis.

-only place with fault surfaces large enough to create magnitude 9 earthquakes.

-can generate giant tsunamis (e.g. those that followed the 2004 Indian ocean earthquake).

OCEANIC-CONTINENTAL SUBDUCTION

-occurs when an oceanic plate dives below a continental plate.

-produces a continental volcanic arc.

Cascade mountains in the pacific northwest

Western Andes mountains in south America

-it is usually the older plate that subducts because it is colder and denser.

-produces an island arc if the volcanoes rise enough to reach the ocean surface.

Aleutian Islands in the northern Pacific Ocean

Lesser Antilles in the Caribbean Sea

COLLISIONS

-occurs when subduction is not possible (e.g. between equally buoyant plates).

-two masses of continental lithosphere slams together.

-no magma formation, no volcanism.

-characterized by tall, non-volcanic mountains; broad zone of frequent, large earthquakes.

TRANSFORM PLATE BOUNDARIES

-places where plates slide past each other in the horizontal plane.

-also called s strike-slip or conservative boundary.

-marked by a large fault, a facture on which sliding occurs.

-movement is described based on the perspective of an observer standing on one of the plates.

Dextral (right-lateral) Sinistral (left-lateral)

-some transform plate boundaries cut continental lithosphere/crust.

San Andreas fault, which cuts across California, defines part of the plate boundary between the north American plate and the pacific plate.

The pacific plate moves northwest, relative to the north American plate.

TRANSFORM FAULTS

-transform faults on the ocean floor connect and offset ridge segments.

-active faulting, as indicated by earthquakes, only occurs in the part of the transform between ridge axes.

-transform faults form at the same time as the initiation of mid-ocean ridges.

-the distance between the ridge segments doesn’t change as seafloor spreading takes place.

TRIPLE JUNCTION

-a place where three plates intersect at a

point.