Presentation on theme: "Geomorphic Processes: I. Endogenic"— Presentation transcript:
1 Geomorphic Processes: I. Endogenic I. Volcanic and Tectonic Processes – Eruptions, Earthquakes,and Landforms
2 Geomorphology – a major subfield of geography – Study of landforms – their origin and change over time and spaceGeomorphic Processes: Physical processes which create and modify landforms on the surface of the earthAre landform changesgradual or abrupt?These processes operatein episodic manner – withearthquakes and volcaniceruptions causing apunctuated equilibrium
3 Geomorphic Processes: A. Endogenic(Endogenous)B. Exogenic(Exogenous)Relates closely to theRock Cycle
4 A. Endogenic ProcessesEndogenic Processes are large-scale landform building and transforming processes– they create relief.1. Igneous ProcessesVolcanism: Volcanic eruptions VolcanoesPlutonism: Igneous intrusionsTectonic Processes (Also called Diastrophism)Folding: anticlines, synclines, mountainsFaulting: rift valleys, graben, escarpmentsLateral Faulting: strike-slip faultsEarthquakes evidence of present-day tectonic activity
6 Igneous Processes– involving eruptions or emplacements of molten magma from the earth’s mantle (extrusive and intrusive igneous rocks)Volcanism : It refers to the extrusion of rock matter from earth’s subsurface to the exterior, and the creation of surface terrain features –Volcanoes are mountains or hills that form in this way.How Volcanoes are FormedAbout 95% of active volcanoes occur at the plate subduction zones and at the mid-oceanic ridges.Subduction is a process of plate tectonics where one lithospheric plate is pushed below another.The other 5% occur in areas associated with lithospheric hot spots.
8 Where are Volcanoes Found? Convergent Plate Boundaries Subduction ZonesOceanic-oceanic island arcsAleutian, Kurile, Marianas, TongaOceanic-continental active continental marginsSouth America, North America, Central America, KamchatkaDivergent Plate Boundaries Mid-Oceanic Ridgesand Rift ValleysContinental-Continental Continental riftsEast Africa, Red Sea-Gulf of AqabaOceanic-Oceanic Oceanic riftsMid-oceanic ridges, spreading sea floors, volcanic islandsIceland, AzoresIntraplate “Hotspots” or “Mantle Plumes”Oceanic islandsHawaii, Emperor Seamount Chains – Pacific OceanContinentalYellowstone, Wyoming, USA
9 Explosive vs. Effusive, depends mainly on temperature and chemical A volcano is generally a conical shaped hill or mountain – some active, others dormant.Built by accumulations of lava flows, and tephra (or fragmented rock material ejected by a volcanic explosion -- also called pyroclastic material, ranging in size from volcanic ash, cinder to volcanic “bombs”Volcanic eruptionsExplosive vs. Effusive, dependsmainly on temperature and chemicaldifferences in the magma silica-rich felsic magma has greaterpotential for explosive eruption basalt-based mafic magma leads tomore effusive eruption
10 Volcanic LandformsVolcanic activity gives rise to such topographic features as:Lava Flows ropy pahoehoe, and blocky aa
11 Volcanic Islandsrelated to hot spots, as in Hawaiirelated to divergent plates and seafloor spreading, as in Iceland
12 Volcanic Mountains (a) Shield, (b) Cinder Cone, (c) Composite Cone or Stratovolcanoand (d) Plug Dome volcanoes + (e) Caldera
13 SHIELD VOLCANOESShield volcanoes are volcanic mountains built up by the eruption of fluid, basaltic lava flowing out of a central vent.They have broad bases with very gentle slopesThe largest shield volcano on Earth is Mauna Loa in Hawaii which rises from itsbase on the seafloorto a height of 17 km(10.5 miles).
14 CINDER CONE VOLCANOESAmboy Crater, southeastern CaliforniaA cinder cone is a steep, conical hill of volcanic fragments that accumulate around and downwind from a ventCinder cones range in size from tens to hundreds of meters tall.
15 COMPOSITE VOLCANOES or STRATOVOLCANOES Stratovolcanoes are very tall, 1000s of feet, and are typical cone-shaped mountainsProduced by alternating layers of felsic and mafic magmas, hence stratas and “Stratovolcano”Most have snow, ice and even glaciers at top because of their heightsEruptions are mostly explosive, but often also effusiveExamples: Mt. Shasta, Mt. Hood,Mt. Rainier, Mt. Fujiyama, Mt. St. Helen
16 Mt. St. Helens a typical composite volcano (before and after 1980 eruption)
17 PLUG DOME VOLCANOES These volcanoes produce thick pasty lava The lava cools into angular blocks after it is slowly squeezed out of the ventsMt. Lassen, northern California
18 CalderaThe most explosive type of volcano is the caldera. The cataclysmic explosion of these volcanoes, and subsequent subsidence, leave a huge circular depression on Earth's surface.Wizard Island and Crater Lake,Oregon
19 WORLD’S LARGEST CALDERA Lake Toba, IndonesiaLargest recognized calderaLake Toba, IndonesiaErupted ~ 75,000 years before present (ybp)Measures 20 miles by 60 milesEjected 2500 km3 of material into atmosphere
21 Long Valley Caldera California Lava flows of the Mono-Inyo Craters volcanic chain in Long Valley Caldera, CaliforniaThe most recent eruptions from this chain occurred about 250 and 600 years agoScientists have monitored geologic unrest in the Long Valley, California, area since 1980The central part of the Long Valley Caldera had begun actively risingUnrest in the area persists today
27 Tectonic Processes – Also called Diastrophism, it relates to: Tectonic forces, which not only move the lithospheric plates, but also cause bending, warping, folding, tilting, and fracturing of earth’s crust at various scales.Such deformation(nature, orientation,inclination andarrangement) ofaffected rock layersis recorded in therock structure
28 Rock StructureNear Golden Gate BridgeSan Francisco, CA
29 Relative to adjacent rock masses, the rock layers may also Relative to adjacent rock masses, the rock layers may also become offset, uplifted, or down-droppedOrientations of inclined rock layers are measured by their strike (compass direction) and dip (angle)
30 Three Types of Tectonic Force and associated types of structural deformation
35 Graben & Horst Topography – Basin and Range Region of western U.S.
36 Shearing Tectonic Forces: Lateral Faulting– strike-slip fault vs. dip-slip faults– San Andreas Fault
37 along the Carrizo Plain in central California San Andreas Faultalong the Carrizo Plainin central California
38 Earthquakes : Evidence of present-day tectonic activity What is an Earthquake?A wave-like sudden vibration or trembling in the Earth – a form of wave energy that travels through the bedrockHappens when accumulated tectonic stress is relieved through sudden, lurching movement of crustal blocks along a fault lineThe motion is caused by quick releaseof seismic waves which travels awayfrom a sub-surface point of sudden energyrelease – the FocusEpicenter is located at the earth’s surfaceimmediately above the focus
39 Seismic Body Waves are of two types: Although most earthquakes occur along plate boundaries or fault lines, they can also be triggered by volcanic eruptions or magma beneath the surface. Earthquakes can precede or accompany volcanic eruptions.Earthquakes shock waves or Seismic Waves travel through the body of the Earth (BODY WAVES) and along the surface (SURFACE WAVES).Seismic Body Waves are of two types:P-waves (Primary waves) are faster, traveling at about 5 km/sThese high-frequency, short waves move through solids and liquidsGround is moved forward and backward as the wave passes throughS-waves (Shear/Secondary waves) half the P-wave speedHigh-frequency, short transverse waves move only through solidsGround is moved upward and downward as the wave passes through
40 Measuring Earthquakes Surface Seismic Waves include Love and Rayleigh wavesLove waves vibrate the ground horizontally – A kind of ‘swaying’ motion is felt at the surfaceRayleigh waves are the slowest of all seismic waves – the ground moves up and down in response to Rayleigh waveMeasuring EarthquakesInstruments are used to record the magnitude of energy released as well as the intensity of shaking by earthquakesSeismographic equipment measures ground motion as a function of timeTwo basic methods of measuring earthquakes are:Richter’s Magnitude Scale: quantitative, objective, 1 – 10Mercalli’s Intensity Scale: qualitative, subjective, I - XII
41 Where Do Earthquakes Occur? Most earthquakes occur in linear belts, along tectonic plate boundaries80% occur around the Pacific Ocean Basin (along the Pacific Ring of Fire)Global Distribution of Magnitude 4.5+ Earthquake Activity,
42 Rupture zones along the San Andreas Fault for each of the three major earthquakes: January 1857 Fort Tejon ▪ April 1906 San Francisco;October 1989 Loma Prieta
43 NORTHRIDGE EARTHQUAKE, 1994 January 17, :31 a.m. 6.7 on Richter ScaleEarthquake occurred on a blind thrust reverse fault (Oak Ridge Thrust Fault system) and produced the strongest ground motions ever recorded in North America
47 CONSEQUENCES OF EARTHQUAKES Displacement on either side of faultVertical and horizontal displacement on Earth’s surfaceSeichesMovement in an enclosed body of water due to intense shaking – Water may actually ‘slosh out’ of the bay or lagoonLiquefactionGroundwater rises to surface and destabilizes soils – buildings collapseTsunamiSeismic sea wave generated by earthquake on ocean floor
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