Chapter 11 MOUNTAIN BUILDING MOUNTAINS THE APPALACHIANS MOUNTAIN BUILDING Occurs via many processes Beautiful majestic mysterious critical How do mountains form How did the valleys and ridges form in this distinct pattern Continental collision Himalayas Subduction zone compression Andes Rifting East African Rift Zone Volcanic mountains Hawaii CONTINENTAL COLLISION Continental crust ends subduction Collision leads to signi cant stress and forces on rocks CONTINENTAL COLLISION Thrust faulting occurs Metamorphic rocks often form THE HIMALAYA TIBETAN PLATEAU Massive collision of Indian sub continent with Asia led to uplift SUBDUCTION ZONES Compression can squeeze crust together leading to uplift This will cause rocks to fold and lead to thrust faults continent EXOTIC TERRANES Dominate the western coast of North America RIFT ZONES Crust pulls apart leading to normal faults Fault blocks rotate leading to sediment basins and ridges Volcanic mountains form due to rising magma EAST AFRICAN RIFT STUDYING MOUNTAIN BUILDING Rocks are deformed by mountain building Rock outcrops yields clues about how mountains were built BRITTLE DUCTILE DEFORMATION Brittle Rocks break Occurs at low temperature pressure Leads to faults joints Ductile Rocks bend Occurs at high temperature pressure Leads to folds BRITTLE DEFORMATION Exotic terranes island fragments of continental crust that are added on to the side of the Fractures and faults cutting through a sequence of sedimentary rock strata developed after deposition of the strata JOINTS Natural crack or fracture resulting from brittle deformation At a normal fault displacement results from the crust being pulled apart e g in a rift No displacement occurs at a joint different than a fault Photo is of a shale cliff face in Ithaca NY FAULTS Fractures in rock where displacement has occurred They are ubiquitous and occur at all scales Show whether rocks were being compressed or pulled apart Strike slip no vertical motion Dipping or dip slip vertical motion FAULT ORIENTATION On a dipping fault the blocks are classi ed as the Hanging wall block above the fault and the Footwall block below the fault Standing in a tunnel excavated along the fault Your head is near the hanging wall block You are standing on the footwall block TYPES OF FAULTS Reverse and thrust faults Hanging wall is pushed up the foot wall Hanging wall is pulled down the foot wall Normal fault NORMAL FAULT zone REVERSE THRUST FAULTS Displacement occurs from compression of the crust Reverse faults are steeper than 35 close to vertical THRUST FAULTS Common in places where uplift is occurring due to continental Collision What kind of faults are these What kind of fault is this Result of normal faulting after an earthquake in Nevada FAULT SCARP HORST GRABEN Result of normal faulting THINGVELLIER GRABEN Iceland A graben is a down dropped block of the Earth s crust resulting from extension or pulling of the crust DUCTILE DEFORMATION Originally horizontal layers folded and distorted by tectonic Activity FOLDS ANTICLINE SYNCLINE Examples of ductile deformation An anticline is a fold that looks like an arch A fold that opens upward like a trough MORE FOLDS Folds reveal something of the process that has shaped rocks in these areas A craton is crust that hasn t been deformed in 1 Ga CRATONS CRATONIC PLATFORMS Sedimentary rock covering old Pre Cambrian basementOhio Geology The Cincinnati Arch THE APPALACHIANS Formed through a series of events