CINDER CONES(TEPHRA CONES) Cinder cones internal layered structure due to varying They show an are small volume cones consisting mainly of tephra that resultafrom strombolian eruptions. They On young cones, depression at the top of the intensities of the explosions that deposit different usuallycalled a of basaltic to andesitic material. cone, consist crater, is evident, and represents the sizes of pyroclastics. controlled by the angle of Slopes of the cones are area above the vent from which material was repose (angle of stable slope for loose unconsolidated material) and ejected. explosively are usually between about 25 and 35o.
Cinder and tephra cones usually occur around summitvents and flank vents of stratovolcanoes.Parícutin Volcano in Mexico. This volcano was born ina farmers corn field in 1943 and erupted for the next 9years.Last eruption:1952
VOLCANIC DOMES (LAVA DOMES) resultfrom the extrusion of highly viscous, gas poor andesitic and rhyolitic lava. Blocks of nearly solid lava break off the outer surface of the dome and roll down its flanks to form a breccia around the margins of domes.
Most dome eruptions are preceded by explosive eruptions of more gas rich magma, producing a tephra cone into which the dome is extruded. They form unstable slopes that may collapse to expose gas-rich viscous magma to atmospheric pressure. This can result in lateral blasts or Pelean type pyroclastic flow (nuée ardentes) eruptions.
SHIELD VOLCANOES by gentle upper slopes (about 5o) andCharacterizedsomewhat steeper lower slopes (about 10o)Most shields were formed by low viscosity basaltic magmathat flows easily down slope away from the summit vent
Vents for most shield volcanoes are central vents, which are circular vents near the summit. Hawaiian shield volcanoes also have flank vents, which radiate from the summit and take the form of en-echelon fractures or fissures, called rift zones, from which lava flows are released.
The term en echelonrefers to closely-spaced,parallel or sub-parallel,overlapping or step-likeminor structural features inrock (faults, tensionfractures), whichlie oblique to the overallstructural trend.
The three main volcanoes which make up the island of Hawaii: Mauna Loa Mauna Kea KilaueaMauna Loa - largest landform on Earth
STRATOVOLCANOES(COMPOSITE VOLCANOES) Stratovolcanoes show than shield volcanoes, with Have steeper slopes inter-layering of lava flows sometimes have a crater at the summit that is formed and pyroclastic material, which is why they are the top o o slopes of 6 to ejection on material from 30central vent by explosive 10 low of the flanks to a near sometimes called composite volcanoes.
Mayon Volcanoit holds the record of the worldsmost perfect volcanic cone.
MAARresult from phreatic or phreatomagmatic activity, whereinmagma heats up groundwater, pressure builds as the waterto turns to steam, and then the water and preexisting rockare blasted out of the ground to form a tephra cone withgentle slopes.
CRATERS AND CALDERAS Craters are circular depressions, usually less than 1 km in diameter, that form as a result of explosions that emit gases and tephra. Calderas are much larger depressions, circular to elliptical in shape, with diameters ranging from 1 km to 50 km. Calderas form as a result of collapse of a volcanic structure.
Formation of the Crater Lake Caldera inEruptions of ash and pumice Southern Oregon Caldera collapse Today Steam explosions
Crater Lake Caldera in southern Oregon is an 8 km diameter caldera containing a lake.
SLOPE LANDFORMSSlope Development Landforms and landscapes change over time as a result of various dynamic factors. These factors include tectonic movement, weather, erosion, and gravity.
BUTTE a prominent isolated hill with steep, often vertical sides and a small, relatively flat top
MESA A (Spanish and Portuguese for "table") is the American Formed by weathering and erosion of horizontally English term for tableland, an elevated area of land with a layered rocks that have been uplifted flat top and sides that are usually steep cliffs. by tectonic activity. In Spanish such a landform is more usually known as a meseta.
PLATEAU another landform that is relatively level, and some sources claim that a plateau is an elevated plain. A plateau has at least one steep, cliff-like side. It forms as a result of geologic uplift (the slow upward movement of large parts of stable areas of Earths crust due to heat forces within the planet) or as a result of much lava flows that spread out over hundreds of thousands of square miles.
CLIFFS usually formed by rock that isa significant vertical, or near resistant rock exposure. vertical, to erosion and weathering.are formed as erosion landforms due to the Sedimentary rocks are most likely that produceprocesses of erosion and weatheringtothem.form sandstone, limestone, chalk, and dolomite. Igneous rocks, such as granite and basalt also often form cliffs.
ARTIFICIAL LANDFORMS An artificial island or man-made island that has been constructed by people rather than formed by natural means.
YAS MARINA ISLAND is an artificial island in Abu Dhabi, UAE near natural Sir Bani Yas island.
THE PALM JEBEL ALI is an artificial archipelago in Dubai, United Arab Emirates which began construction in October 2002, was originally planned to be completed by mid 2008 and has been on hold since
HARBOR ISLAND is an artificial island in the mouth of Seattle, Washingtons Duwamish Waterway where it empties into Elliott Bay. was then the largest artificial island in the world, at 350 acres (1.4 km²).