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