3. Landforms related to different types of movements Faults / Zlomy 3 types of faults – under different stress regimes (napěťových režimech): poklesové zlomy (normal fault), přesmykové zlomy (reverse fault, thrust fault), zlomy s horizontálním posunem (strike-slips); video!Repeated earthquakes or creep – relief formation normal fault (pokles) reverse fault (přesmyk)thrust fault (násun) Strike-slips San Andreas fault Piqiang fault Some features indicate the presence of a fault, but say little about activity or type of movements: vegetation alignments, springs, fault scarps, other lineaments Change in landscape caused by change in landscape process (e.g. increased slope on alluvial fan - ? tectonic or sedimentary process?) Tectonic geomorphology - looks for morphological anomalies – surfaces warped, tilted, uplifted, fractured Fundamental principle of geomorphology: Gilman Hot Springs, San Jacinto Valley All Fault Types Have Potential to Disrupt Groundwater Flow (narušení toku podzemních vod) Springs – fault gouge (tektonický jíl) - effective barier Linear springs San Andreas Fault -Thousand Palms Oasis, Indio Hills, California • Vegetation Lineaments (arid areas) Scarps (zlomové svahy) – all fault types, all scales Northward across Coyote Creek Fault, San Jacinto Fault Zone Carboneras fault, Spain A young scarp!! Scarp on strike-slip (oblique slip) Coyote Mts, Elsinore fault, CA Scarps on normal fault Krupnik fault , Bulgary, 1904 M=7,8 Scarps on thrust/reverse fault (přesmyk) Chichi earthquake 1999, Taiwan Active or Inactive? • Differential weathering along inactive faults can produce features that resemble features produced by active faults – Vegetation lineaments – Linear valleys - Scarps (výrazné terénní stupně) “Fault-Line Scarps” (svah na zlomové čáře) „Fault Scarps“ (zlomový svah) „Complex fault scarp“ (složený zlomový svah) Some geomorphic features clearly indicate young activity (usually Holocene to late Quaternary) • If it is expressed in the geomorphology, it is likely active (unless you can demonstrate that the features are totally erosional in nature) - scarps in alluvium, deflected drainages, sags, shutter ridges, side-hill benches Christchurch EQ 21.2. 2011, M = 6.3, NZ - unknown fault, uplift of Southern Alps – 10mm/year =high sedimentation, sediments obscure the fault trace A general rule is that active faults produce alluvium so they bury themselves, so locally, the evidence for activity may be obscured along some portions of the fault Active Strike-Slip Fault Geomorphology Burbank and Anderson, 2001 Effects on Stream Channels Offsets • Implies a previously straight, now-curved channel as a result of displacement • the bend in the channel must agree with the sense of slip! Deflections • The curve in the channel can be with or against the sense of slip • Result of drainage capture – (water will take the easiest path downhill, alluvial fans) All offsets are deflections, but not all deflections are offsets! Offset channels Pitman Canyon ~ 46 m offsets San Andreas Fault, Carrizo plain, CA Wallace creek Offset/Deflected channels Carizzo plain Superstition Hills fault 0 40 km Coyote Mts 0 10 km Coyote Mts extension sag pond offset valley side beheaded channels 15m Elsinore fault, Coyote Mts, CA 15m beheaded channels 5-8m cumulative slip offset and beheaded channel 2m fault 0 500 m Offset alluvial fans Elsinore fault, Coyote Mts, CA Alverson canyon, offset valley side 0 40 m 0 50m offset channels and bars offset channel bars offset alluvial fan 150m offset alluvial fan Different lithology – tells us about the amount of offset offset channel Laguna Salada fault, 2010, M= 7.2 El Mayor offset channel offset valley side Kunlun fault, Tibet, 2001 M = 7.8 San Jacinto Fault, Southern California Offset Channel sag sag Offset channel margin piercing/matching points Shutter Ridge • Ridge moved and blocked the drainage Drainage Shutter Ridge(s) blocking drainage Clark strand of the San Jacinto Hector Mine Rupture, 1999 San Jacinto Fault, Southern California Shutter Ridge(s) Linear valleys Linear valleys - related to faulting or just fault-line eroding crushed fault zone rocks Transtension/Transpression Transtension • Simultaneous occurrence of strike-slip faulting and extension Transpression • Simultaneous occurrence of strike-slip faulting and shortening •Both occur at all scales! Local to regional features •Controlled by bends in SS fault (local), or overall convergence/divergence along a SS fault (regional) Transtension • Component of divergence along SS fault (strike-slip) • Right steps in Dextral (pravostranný) SS fault • Left steps in Sinistral (levostranný) SS fault Opening causes a “sag,” or pull-apart basin San Andreas Sag Ponds Topographic depression produced by extensional bends or stepovers along a strike-slip fault. It may or may not contain water year-round. Synonymous with pull-apart basin. Transpression • Component of convergence along SS fault • Left step in Dextral SS fault • Right step in Sinistral SS Fault Right-step causes a space problem, and a “pressure ridge” is formed Small pressure ridge along SAF in Cholame Valley Pressure ridge A topographic ridge produced by compressional bends or stepovers along a strike-slip fault Dragon’s Back Pressure Ridge System along the San Andreas Thousands Palms – Indio Hills, San Andreas fault Pressure ridge Denali fault, 1964, M=8,5 Kunlun fault, Tibet, 2001 M = 7.8 „Mole track“ structure Material is extruded along the fault by pressure SAF, San Francisco 1906, M = 7.9 Denali fault, Alaska Side-Hill Benches/Valleys Parallel faults, Kresna Gorge, Bulgary Slope inflection along San Andreas Fault Flat step on the slope Geomorphology of Extensional Faulting: normal fault Zanjan. Iran Extensional Faulting Displacement accommodated in normal faults Single, Parallel synthetic, Antithetic Primary normal fault (60-70) Crustal penetrating fault Often has km of displacement Separates linear mountain range from adjacent basin Up-faulted block (horst) Down-faulted block (graben) Crustal extension and normal faults – related to the most remarkable topography at regional scale Rifts valleys rift – elevated heatflow, vertical compression, horizontal extension East African Rift Valley East African rift in 20 mil years active divergence, rift – numerous of normal faults Hayli Gubbi, shield volcano, crater inside caldera, Afar region, Ethiopia Normal faults disecting the volcanos, Afar Rift activity 2009 Massive fissure splits open in the Ethiopian Desert Main Ethiopian Rift Valley Escarpments Rift Valley - Tanzania They has been formed during millions years Iceland - shaded area shows the Icelandic Basalt Plateau, red points the migration of the hot spot and orange lines are the rifts, both active and inactive. Iceland – Rift Valley ridge represents submarine segments of the mid-ocean ridge Rift valley, Thingvellir national park, Iceland Geological map of Iceland volcanic systems and volcanic zones and the division of the island into formations. Each volcano with the typical lifetime of 0.5-1.5 my. Around 30 active volcanic systems in Iceland. Mid-Atlantic oceanic ridge Ocean ridge – basaltic oceanic crust Basin and Range topography broad extensional faulting Basin and Range Province extension and thinning of the lithosphere, listric faults, grabens, horsts elevated heat flow, geothermal energy From Sierra Nevada to Wasatch Mts – 800 km „Local scale„ normal faults Fault trace of normal faults tends to be short 10- 50 km The Wasatch fault, forms the eastern boundary of the Basin and Range geologic province frontal fault are up to 400 km long, composed of separate faults or segments 30 – 60 km long, average of 40 km, each of which can independently produce earthquakes as powerful as local magnitude 7.5 Linear mountain fronts The Wasatch Mountains have been uplifted and tilted to the east by movement of the fault. The average rate of uplift along the fault over its history is approximately 1 mm per year. Wasatch Mts Linear mountaint front - repeated earthquakes Scarp on the southern part of the Nephi strand of the Wasatch fault: Multiple fault scarps (marked by arrows) cut across 16,000 to 18,000-year-old glacial moraines in Salt Lake County. Some of the scarps are 30 to 40m high, indicating they were formed by repeated large earthquakes (possibly as many as seven to ten events) in the past 18,000 years Wasatch fault un-named fault in California, SE from Panamint Valley Triangular (trapezoidal) facets - dissected mountain front by rivers, setries of facets - „flatirons“ Subsided blocks San Gorgonio Pass Narrow block subsided between two ridges uplifted by strands of San Andrea Fault sags and ridges – by uneven blocks uplift Crustal shortening + thickening • Crustal shortening is the reduction of the size of the Earth's crust through convergent plate boundary (compression) Reverse Faulting, Folding and Uplifting Crustal Shortening • Implications : - Reverse/Thrust Fault - Fold - Uplift Reverse – Thrust/overthrust Fault Reverse Fault : > 450 Menší slip – větší reliéf, ale menší oblast postižena <450 Video! Thrust faults associated with subduction produce a variety of landforms – - uplifted coastal terraces, anticlinal hills (upwarped) and synclinal lowlands (downwarped) Thrust faults – often associated with fold - in fold-and-thrust belts - some of the thrusts and reverse fault may break the surface or they remain hidden in the core of anticline – blind reverse fault Reverse faults- closely related to folds Rate of lateral propagation of faults and fold may be several times higher than vertical slip rate of the fault Asymmetric fault-propagation fold developed over a décollement Landforms associated with reverse faulting steep mountain fronts, fault scarps, fold scarps, extensional features, and landslides 1980 EL Asnam M=7.3, Algeria – fold-and-thrust belt 3-6 m slip on reverse fault at the depth, surface rupture - 2m mostly anticlinal uplift of 5m – seismic folding a),b),c ) hanging-wall folding d) extensional features produced by component of left-lateral shear c) tension fractures a) elongated en echelon depressions b) footwall folding and flexural-slip faulting Graph of surface uplift produced by 1980 El Asnam EQ. The fold was produced by repetaed earthuqakes Bolcked river – formation of a lake with deposition of 0.4 m Fault scarps Fold Thompson and Turk, 1998