Physical Geography by Alan Arbogast Chapter 13 Tectonic Processes and Landforms Lawrence McGlinn Department of Geography State University of New York - New Paltz © 2007, John Wiley and Sons, Inc.

Tectonic Processes and Landforms Plate Tectonics Types of Plate Movement Plate Convergence Earthquakes Volcanoes © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

Fossil Evidence for Pangaea © 2007, John Wiley and Sons, Inc.

Continental Drift Since Pangaea © 2007, John Wiley and Sons, Inc.

Mechanisms of Continental Drift Magma Plume pushes plates apart Convection within Earth © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Seafloor Age Red youngest through green & yellow to blue, oldest © 2007, John Wiley and Sons, Inc.

Current Locations & Movement of Plates © 2007, John Wiley and Sons, Inc.

Types of Plate Movements Passive Plate Margins Transform Plate Margins Plate Divergence Plate Convergence Collision Subduction © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

Transform Plate Margins Boundaries where plates slide past each other horizontally © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Rifting in East Africa © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Collision and Folding Folding © 2007, John Wiley and Sons, Inc.

Ridge and Valley Evolution The Folded Appalachians © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Subduction Process in which one converging plate is forced beneath another, usu. oceanic plate under continental Plate Boundary Relationships © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Earthquake Processes © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

Triangulation to Locate ‘Quake Known distance to stations A, B and C shows location of epicenter © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Seismograph Records vertical & horizontal motion of Earth, & magnitude of motion © 2007, John Wiley and Sons, Inc.

Measuring Earthquakes Richter Scale – logarithmic measure where each whole number represents 10X the shaking of the next smaller number © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Fault Types Earthquake © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. San Andreas Fault (Transform Fault) Movement © 2007, John Wiley and Sons, Inc.

Basin and Range Province From Satellite Horst & Graben Formation In Landscape © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

Cinder-Cone Volcanoes Small, steep-sided volcano made of magma fragments & rock debris from central vent © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Composite Volcanoes Large, steep-sided volcano built up by layers of lava & rock debris – over subduction zones – viscous (low flow), silicate (high gas-explosive think of shaking coca-cola can) magma - explosive eruptions Cross Section Mt. Fuji © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Pacific “Ring of Fire” Concentration of composite volcanoes around the Pacific Basin over subduction zones © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Shield Volcanoes Broad, gentle-sided volcanoes formed from low-silica, low-viscosity (high flow) magma – lava flows cool & harden to become basalt Cross Section Mauna Loa, Hawaii © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. 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 © 2007, John Wiley and Sons, Inc.

Formation of Hawaii Emperor Seamount Chain Hawaii 70 M yrs old – Pac. Plate 1st moved North, then NW Hawaii Kauai Oldest – Big Island (Hawaii) still over hot spot 70 mya Present © 2007, John Wiley and Sons, Inc.

Yellowstone Hot Spot North American Plate has moved west, then northwest over past 16.5 M yrs Calderas from eruptions in past 2 M yrs © 2007, John Wiley and Sons, Inc.

© 2007, John Wiley and Sons, Inc. Geyser Cross Section Old Faithful © 2007, John Wiley and Sons, Inc.