PHYSICALGEOG UNIT FOUR

Slide1: 

Physical Geography by Alan Arbogast Chapter 12 Earth’s Internal Structure, Rock Cycle, and Geologic Time Lawrence McGlinn Department of Geography State University of New York - New Paltz

Earth’s Internal Structure, Rock Cycle, and Geologic Time: 

Earth’s Internal Structure, Rock Cycle, and Geologic Time Earth’s inner structure Rocks and minerals in the Earth’s crust Geologic time Basic geomorphology of continents and ocean basins

Earth’s Inner Structure: 

Earth’s Inner Structure Major Layers (outside-in): Lithosphere Upper Mantle Lower Mantle Outer Core Inner Core

Inner Core: 

Inner Core Radius 760 mi. Mostly solid iron w/bit of nickel Temp 3200º-5200º C Tremendous pressure keeps inner core solid

Outer Core: 

Outer Core 1398 mi. thick Outer core is liquid – molten iron Similar temp to inner core, but less pressure Generates >90% of Earth’s magnetic field Magnetosphere protects Earth from solar wind Mag. field likely due to circulation in outer core that create electrical currents

Mantle: 

Mantle Surrounds core Solid iron, magnesium, silicon oxides Lower mantle – 1385 mi. thick Lower mantle cooler than outer core, so solid Upper mantle – 260 mi. thick Upper mantle mostly viscous nickel – like syrup Upper part of upper mantle is Aesthenosphere

Aesthenosphere: 

Aesthenosphere 25-105 mi. below surface Zones of molten rock heated by radioactive decay make up 10% of aesthenosphere These zones basis of plate tectonics, earthquakes, volcanoes, mtn building

Lithosphere: 

Lithosphere Uppermost layer of the Earth Extends from surface down into aesthenosphere (44 mi.) Upper part of lithosphere is crust, brittle exterior of Earth 5-25 mi. thick Mohorovocic Discontinuity (Moho) – boundary between crust and aesthenosphere

Earth’s Outermost Layers: 

Earth’s Outermost Layers Oceanic Crust – ~5 mi thick – mostly basalt - dense Continental Crust - ~25 mi thick – mostly granite – less dense

Rocks & Minerals in Earth’s Crust: 

Rocks & Minerals in Earth’s Crust Minerals – naturally occurring substances with distinctive chemical & atomic configurations usually in crystalline form Rock – formed by minerals bonded together in a solid state – usually 2 or more minerals bound together 3 types : Igneous, Sedimentary & Metamorphic

Igneous Rock: 

Igneous Rock Formed from cooled magma – liquid rock from aesthenosphere Largely silicate minerals – silicon & oxygen Extrusive igneous rock – from cooled lava – liquid rock extruded onto Earth’s surface Intrusive igneous rock – from cooled magma intruded into older rock in crust Pluton – body of intrusive igneous rock

Sources of Igneous Rock: 

Sources of Igneous Rock

Silicate Minerals in Igneous Rock: 

Silicate Minerals in Igneous Rock Felsic Rock Mafic Rock

Sedimentary Rock: 

Sedimentary Rock Vast amts of formerly loose minerals (sediment) deposited in layers Sediments cement to each other in process called lithification - water is squeezed out by weight of overlying deposits & minerals recrystallize 3 Types: Clastic – from rock or mineral fragments Chemical – from mineral precipitates Organic – from carbon-based organic matter

Sedimentary Rock Formation in Marine Environments: 

Sedimentary Rock Formation in Marine Environments

Clastic Sedimentary Rock Examples: 

Clastic Sedimentary Rock Examples Conglomerate – type of Sandstone from various size sediments, some large Navajo Sandstone – from ancient sand dunes Shale – from mud deposits Clastic Rocks

Chemical Sedimentary Rock Formation: 

Chemical Sedimentary Rock Formation Whitish haze around these Bahama Islands (aerial view) is made up of carbonate minerals precipitating in shallow waters Rock Types : Limestone – Calcium Carbonate Dolomite – Calcium-Magnesium-Carbonate

Organic Sedimentary Rocks: 

Organic Sedimentary Rocks Coal – from plant and organic matter deposited in cool wetlands, forming peat – over time overlying layers of sediment compress & heat peat into coal “Overcooked” deposits become petroleum Natural gas – from microscopic plants at surface of sea water – decompose to gas

Metamorphic Rocks: 

Metamorphic Rocks From igneous & sedimentary rock under great heat & pressure for millions of years Examples of igneous & sedimentary rocks becoming metamorphic: Shale → Slate → Schist Limestone → Marble Sandstone → Quartzite

Types of Metamorphism: 

Types of Metamorphism

The Rock Cycle: 

The Rock Cycle The Rock Cycle

Geologic Time: 

Geologic Time Earth’s history (4.5 B years) divided into: Eons Eras Periods Epochs Radiometric Dating – compare amt of radio-active isotope to amt of decayed end product in a rock to estimate its age The Geologic Time Scale

Geologic Time as a Year: 

Geologic Time as a Year

Geologic Time Markers: 

Geologic Time Markers

Evolution of Spanish Peaks: 

Evolution of Spanish Peaks Sediment deposited & sedimentary rocks form Sangre de Cristo Mts form as magma intrudes Sedimentary rock erodes as Spanish Peaks emerge

Geomorphology of Continents and Ocean Basins: 

Geomorphology of Continents and Ocean Basins Geomorphology – study of formation, shape, distribution, & evolution of landforms on Earth Landform – a distinct geographic feature such as a mountain, river valley, coastline, or sand dune Continents consist of 2 basic geomorphic regions: Alpine Chains & Continental Shields

Continental Shelf: 

Continental Shelf Earth’s land area increases dramatically (from 29% to 35% of Earth’s surface) if sea level falls as in a previous glaciation (1.6 my ago) because of the relatively shallow continental shelf.

Alpine Chains: 

Alpine Chains Belts of active mountain building due to volcanic or tectonic processes

Continental Shields: 

Continental Shields Geologically inactive regions with low relief made of old, stable, igneous or metamorphic rock

Slide30: 

Physical Geography by Alan Arbogast Chapter 13 Tectonic Processes and Landforms Lawrence McGlinn Department of Geography State University of New York - New Paltz

Tectonic Processes and Landforms: 

Tectonic Processes and Landforms Plate Tectonics Types of Plate Movement Plate Convergence Earthquakes Volcanoes

Plate Tectonics: 

Plate Tectonics Theory that Earth’s crust consists of plates that move individually & collectively Helps explain location of mtn ranges, earth-quakes, volcanoes & other landforms First theorized by Wegener in early 1900s Pangaea – supercontinent that existed 300 my ago – continents spread by Continental Drift Theory ignored through 1950s – validated in more recent research

Fossil Evidence for Pangaea: 

Fossil Evidence for Pangaea

Continental Drift Since Pangaea: 

Continental Drift Since Pangaea Continental Drift

Mechanisms of Continental Drift: 

Mechanisms of Continental Drift Convection within Earth Magma Plume pushes plates apart

Seafloor Age: 

Seafloor Age Red youngest through green & yellow to blue, oldest

Current Locations & Movement of Plates: 

Current Locations & Movement of Plates

Types of Plate Movements: 

Types of Plate Movements Passive Plate Margins Transform Plate Margins Plate Divergence Plate Convergence Collision Subduction

Passive Plate Margins: 

Passive Plate Margins Where continental crust and bordering oceanic crust are on the same tectonic plate – tectonically stable Example of East Coast of US on North American Plate

Transform Plate Margins: 

Transform Plate Margins Boundaries where plates slide past each other horizontally

Plate Divergence: 

Plate Divergence Lithospheric plates moving away from each other Magma plumes move up & out through plate fractures, plates spread in process called Rifting As plates spread, Mid-Oceanic Ridge forms from rifting Active and Passive Margins

Rifting in East Africa: 

Rifting in East Africa

Plate Convergence: 

Plate Convergence Collision – two plates of continental crust meet Crust crumples causing folding of horizontal bedrock layers Monocline – 1-sided slope rock beds inclined in one direction over large area Anticline – upward arc of folded rock Syncline – downward dip in folded rock Overthrust fault – intense compression shoves one part of rock mass over the other

Collision and Folding: 

Collision and Folding Folding

Ridge and Valley Evolution: 

Ridge and Valley Evolution The Folded Appalachians

Subduction: 

Subduction Process in which one converging plate is forced beneath another, usu. oceanic plate under continental Plate Boundary Relationships

Earthquakes: 

Earthquakes Sudden release of tectonic stress creates movement in Earth’s crust & shockwaves through lithosphere Fault – fracture between adjoining plates along which plates can move Focus – point in lithosphere where fault breaks Epicenter – point on surface directly above focus

Earthquake Processes: 

Earthquake Processes

Earthquake Energy: 

Earthquake Energy Waves released by an earthquake: P-waves – primary, compressional waves that travel 1.5-8 km/sec S-waves – secondary, vertical waves that travel 60-70% slower than P waves Difference in arrival time of p-waves and s-waves, helps estimate distance to epicenter Known distance to 3 stations yields location

Triangulation to Locate ‘Quake: 

Triangulation to Locate ‘Quake Known distance to stations A, B and C shows location of epicenter

Seismograph: 

Seismograph Records vertical & horizontal motion of Earth, & magnitude of motion

Measuring Earthquakes: 

Measuring Earthquakes Richter Scale – logarithmic measure where each whole number represents 10X the shaking of the next smaller number

Faulting: 

Faulting Earthquakes occur along faults – cracks in Earth’s crust where rocks or plates are displaced Fault Types: Normal – vertical fault, diverging force Reverse – vertical fault, compressional force Strike-Slip – horizontal fault, blocks slide past one another – larger scale called Transform Overthrust – upthrown block slides over downthrown block

Fault Types : 

Fault Types Earthquake

San Andreas Fault: 

San Andreas Fault (Transform Fault)

Basin and Range Province: 

Basin and Range Province Horst & Graben Formation From Satellite In Landscape

Volcanoes: 

Volcanoes Mts or hills w/ a conduit down into upper mantle through which magma, ash & gases are ejected 3 basic types: Cinder-cone Volcanoes Composite Volcanoes Shield Volcanoes Volcanoes

Cinder-Cone Volcanoes: 

Cinder-Cone Volcanoes Small, steep-sided volcano made of magma fragments & rock debris from central vent

Composite Volcanoes: 

Composite Volcanoes Large, steep-sided volcano built up by layers of lava & rock debris – over subduction zones – viscous, silicate magma - explosive eruptions Cross Section Mt. Fuji

Pacific “Ring of Fire”: 

Pacific “Ring of Fire” Concentration of composite volcanoes around the Pacific Basin over subduction zones

Shield Volcanoes: 

Shield Volcanoes Broad, gentle-sided volcanoes formed from low-silica, low-viscosity magma – lava flows cool & harden to become basalt Cross Section Mauna Loa, Hawaii

Hot Spots: 

Hot Spots Stationary points in aesthenosphere from which a magma plume intermittently pushes through the crust above Plates move over hot spots, carrying deposits of basalt with them Hawaii (& the Emperor Seamount Chain) & Yellowstone have been shaped by hotspots

Formation of Hawaii: 

Formation of Hawaii Emperor Seamount Chain 70 M yrs old – Pac. Plate 1st moved North, then NW Hawaii Kauai Oldest – Big Island (Hawaii) still over hot spot

Yellowstone Hot Spot: 

Yellowstone Hot Spot North American Plate has moved west, then northwest over past 16.5 M yrs

Geyser Cross Section: 

Geyser Cross Section