July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 1 Mountains and Mountain Building

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 2 Orogenesis Orogenesis is the process of building a mountain range Most mountain ranges are products of plate tectonics and the interactions at plate boundaries –Type of mountains is determined by the type of plate boundary –Divergent boundaries produce fault-block mountains; convergent boundaries produce folded mountains

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 3 Fault-Block Mountains Fault-Block Mountains are produced during rifting –Tension pulls the plates apart, creating Normal Faults and Listric Faults –In a Normal Fault, the “Hanging Wall” moves down relative to the “Footwall” –A Listric Fault is a curved Normal Fault

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 4 Fault-Block Mountains Fault-Block Mountains are also known as a Horst-Graben Landscape –Horst is the high plateau –Graben is the valley section that dropped down after faulting

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 5 Folded Mountains Folded Mountains are the result of compression at convergent boundaries –Sometimes are called “Complex” Mountains due to the complex structures –Structures include: Thrust Faults Folds Plunging Folds Igneous/Metamorphic Belts (usually, but not always – Rockies don’t have one, for example)

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 6 Thrust Faults In a thrust fault, older rocks are “thrust” up and onto younger rocks Due to the compression of the crust during a collision –Like a car crumpling during a crash

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 7 Thrust Faults

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 8 Folds The collision of continents leads to deformation of the rocks Deformation is changing the shape and/or orientation of the rock beds Deformation is caused by increased pressure and/or temperature – Folds are the result of long-term pressure applied to a region – Small folds can result when pressure is applied to heated rock beds

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 9 Folds Large and Small Folds…

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 10 Types of Folds Anticlines – fold where the oldest rocks are found in the center –Shaped like a letter “A”

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 11 Types of Folds Synclines – folds where the youngest rocks are found in the center –Shaped like a letter “U” –Often found together with an anticline

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 12 Types of Folds Monoclines – fold with only one turn –either upward and then flat or downward and then flat

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 13 Folds

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 14 Complex Folds Overturned folds occur when a rock units are so compressed that a fold tips in one direction Several overturned folds on top of each other are called recumbent folds –Like a skidding on a carpet

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 15 Complex Folds Plunging folds are tilted with respect to the surface of the Earth and appear to dip into or out of the surface

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 16 Plunging Folds

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 17 Igneous/Metamorphic Belts At the hearts of most folded mountain ranges are belts of igneous and/or metamorphic rocks –Due to the convergent boundary –Igneous and metamorphic rock come from volcanic and plutonic activity due to the subduction of the oceanic plate –Belts are usually narrow ( miles wide)

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 18

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 19 Anatomy of Folded Mountains Thrust Faults Thrust Faults Igneous and Metamorphic Rocks Folded Rocks Accretionary Prism Suture Mélange

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 20 Exotic Terranes Exotic terranes are landmasses that are sutured onto a continent during collisions They can be large or small Most of western North America was formed by suturing exotic terranes onto the North American craton during the Cenozoic Leads to narrow ranges of unique mountains

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 21 Other Types of Orogenesis Some mountain ranges are the product of regional uplift where the land is forced up and rivers cut through the land –Adirondack Mountains in NY are an example –Mountains can also be carved by wind or glaciers

July 2, 2016July 2, 2016July 2, 2016 AF Carpinelli 22 Domes and Basins Domes and Basins are circular features caused by the large-scale erosion of an anticline or syncline –In a dome, the oldest rocks are in the center –In a basin, the youngest rocks are in the center