The Nature of Volcanic Eruptions Magmas Composition Temperature
- Slides: 85
The Nature of Volcanic Eruptions
• Magma’s Composition • Temperature • Dissolved Gases
Mobility or Viscosity (viscos=sticky)
The more viscous the material, the greater its resistance to flow Magma’s viscosity is due to its silica content Silica impedes the flow of magma because silicate structures start to link together The more silica in magma the greater the viscosity Amount of volatiles (gaseous component, mainly water) affects the mobility of magma Rhyolitic (felsic lavas) – very viscous, form thick short, thick flows Basaltic lavas – more fluid, travel up to 150 km
�Temperature �Chemical Composition Factors affecting Viscosity
Why do volcanoes erupt?
Most magma is generated by partial melting in the upper mantle to form molten material (basaltic) Once formed the buoyant molten rock rises to the surface Density of crustal rocks decreases when closer to the surface, ascending basaltic magma may reach a level where rocks are less dense Formation of a magma chamber occurs As magma body cools, minerals with high temperatures crystallize first, leaving remaining melt enriched in silica. Some molten Material may ascend to the surface to produce a volcanic eruption
Hawaiian Type Eruptions
• Magma mobilizes and quickly moves upward along the newly buoyant plumes called eruption columns that extends thousands of meters in the atmosphere • Bubbles grow by - continued separation of gases from the melt - expansion of bubbles as confining pressure drops
� Volatiles tend to be most abundant near tops of magma reservoirs containing silica rich melts � Viscosity of magma + dissolved gases = nature of volcanic eruption � Basaltic magmas – smaller gaseous component and permit fluid and gentle flow of lava � Silica-Rich magmas – more gaseous component, explosive
MATERIALS EXTRUDED DURING AN ERUPTION
Volcanoes extrude : vlava vlarge volumes of gas vpyroclastic materials
v. Lava Flows Ø Lava - is molten rock that flows out of volcanoes Ø CATEGORIES OF LAVA : 1. Basaltic - is comprised of the least amount of silica. It is the fastest flowing lava. Basaltic lava is commonly expelled from shield volcanoes. 2. Andesitic - It has a higher viscosity than basaltic lava and thus flows at a slower rate. Its flow is described as block flow. 3. Rhyolitic - has the highest viscosity, It flows much slower than andesitic and basaltic lava.
Basaltic Lava Andesitic Lava Ryolitic Lava
Two Types of Lava Flows : aa Flows have surfaces of rough jagged blocks with dangerously sharp edges and spiny projections. Pahoehoe Flows exhibit smooth surfaces that often resemble the twisted braids of ropes. Pahoehoe means “on which one can walk. ”
Lava Tubes v. Hardened basaltic flows commonly contain cave-like tunnels that were once conduits carrying lava from the volcanic vent to the flow’s leading edge. v. Lava tubes are important features because they serve as insulated pathways that facilitate the advance of lava great distances from its source.
GASE S q Magmas contain varying amounts of dissolved gases(volatiles) held in the molten rock by confining pressure. q The gaseous portion of most magmas makes up from 1 to 6 percent of the total weight, with most of this in the form of water vapor.
Pyroclastic Materials • When volcanoes erupt energetically they eject pulverized rock, lava, and glass fragments from the vent. • The particles produced are referred to as pyroclastic materials (pyro = fire, clast = fragment)
Volcanic Ash Block Scoria Welded Tuff Lapilli Bomb Pumice
Volcanic Structures and Eruptive Styles
ANATOMY OF A VOLCANO
Types of Volcanoes Shield volcano • Broad, slightly domed-shaped/ resembles a Warrior's shield • Composed primarily of basaltic lava • Generally cover large areas • Produced by mild eruptions of large volumes of lava
Mauna Loa : A Classic Shield Volcano
Kilauea, Hawaii : Eruption of a Shield Volcano
Cinder cone • Built from ejected lava (mainly cinder-sized) fragments • Steep slope angle • Rather small size • Frequently occur in groups
Paricutin: Life of a Garden-Variety Cinder Cone
Composite cone (Stratovolcano) • Most are located in a relatively narrow zone that rims the Pacific Ocean, appropriately called the Ring of Fire. • Large, classic-shaped volcano (1000’s of ft. high & several miles wide at base) • Composed of interbedded lava flows and layers of pyroclastic debris.
Fujiyama , Japan
Nuée Ardente: A Deadly Pyroclastic Flow • Pyroclastic flows, which consist of hot gases infused with incandescent ash and larger lava fragments. Also referred to as nuée ardentes (glowing avalanches), these fiery flows are capable of racing down steep volcanic slopes at speeds that can exceed 200 kilometers (125 miles)per hour.
Mt. Mayon
In addition to violent eruptions, large composite cones may generate a type of very fluid mudflow referred as lahar. These destructive flows occur when volcanic debris becomes saturated with water and rapidly moves down steep volcanic slopes, generally following gullies and stream valleys.
Other Volcanic Landforms • Calderas (caldaria. = a cooking pot) are large depressions with diameters that exceed one kilometer and have a somewhat circular form. Calderas are formed by the following processes: (1) Crater Lake-type calderas (2) Hawaiian-type calderas (3) Yellowstone-type calderas
Fissure Eruptions and Basalt Plateaus • The greatest volume of volcanic material is extruded from fractures in the crust called fissures (fissure: = to split).
Volcanic pipes and necks • Pipes are short conduits that connect a magma chamber to the surface • Volcanic necks are resistant vents left standing after erosion has removed the volcanic cone
Shiprock, NM – a volcanic neck
Intrusive igneous activity
Tabular intrusive bodies • Dikes – forms when rising magma vertically cuts across the sedimentary beds • Sills _ forms when magma enters through a weak portion of the sedimentary bed horizontally
Massive intrusive bodies • Batholiths – intrusive rocks that exposure of over 100 square kilometers have a surface • Stocks – similar to a batholite but has less surface exposure. • Laccoliths – happens when rising magma lifts up the sedimentary bed that it penetrated.
Origins of Magma
From solid rocks • Increase in temperature • Decompression Melting • Addition of Volatiles
Partial Melting and Magma Compositions • As rocks are heated minerals with lower melting points melt first, melted rocks that turn into magma then melts other rocks that have higher melting points.
Plate Tectonics and Volcanic Activity
• Volcanism at Convergent Plate Boundaries • Volcanism at Divergent Plate Boundaries • Intraplate Volcanism
Living with Volcanoes
Volcanic Hazards • Pyroclastic flows • Lahars • Explosive eruptions
Monitoring Volcanic Activity • Changes in the pattern of volcanic earthquakes • Expansion of near-surface magma chambers
• Changes in the amount of gases that are released • Increase in ground temperature
FAULTS AND FRACTURES
FAULTS AND FRACTURES • Faults are fractures in the crust along which appreciable displacement has taken place. • Is a fracture or zone of fractures between two blocks of rocks
TYPE OF FAULTS
DIP SLIP OR NORMAL SLIP
STRIKE SLIP FAULTS
THRUST FAULT
Continental Collisions
Continental Collisions results in the development of mountains characterized by shortened and thickened crust achieved through folding and faulting.
The Himalayas are the youngest collision mountains on Earth and are still rising. (India began to collide with Asia)
Shilla Peak in the Himalayas, northeastern Himachal Pradesh State, India Himalayas Glaciers: Zaskar Range of Jammu and Kashmir State, Northern India
The collision between India and Asia that generated the Himalayas and Tibetan Plateau also severely deformed much of Southeast Asia. a. ) Map view of some of the major structural features of Southeast Asia thought to be related to this episode of mountain building. b. ) Re-creation of the deformation of Asia, with a rigid block representing India pushed into a mass deformable modeling clay.
The Appalachians indicates that the formation of this mountain belt was complex and resulted from three distinct episodes of mountain building.
Three Episodes of Mountain Building 1. Taconic Orogeny – the collision that ensued between 450 and 500 million years ago. Deformed the continental shelf and sutured the crustal fragment to the North American Plate. The metamorphosed remnants of the continent fragment are recognized today as the crystalline rocks of the Blue Ridge and Western Peidmont regions of the Appalachians. 2. Acadian Orogeny – began about 400 million years ago. The continued closing of the ancestral North Atlantic resulted in the collision of the developing island arc with North America. 3. Final Orogeny – between 250 and 300 million years ago, when Africa collided with America.
CRUSTAL DEFORMATION AND MOUNTAIN BUILDING
CRUSTAL DEFORMATION
- üledékes kőzetek csoportosítása
- Magmas dosage form
- Flowchart of matter
- Difference between curie temperature and neel temperature
- Difference between curie temperature and neel temperature
- Ferromagneti
- Nature and nature's law lay hid in night meaning
- Nature nature controversy
- Volcanic ash
- Volcanic belts form along _____.
- Thin layers of volcanic ash act as excellent time markers
- Volcanic rupture
- Volcanic formations
- Volcanic rocks and plutonic rocks
- Volcanic ash
- Chapter 18 volcanic activity
- Volcanic island arc
- Primary volcanic hazards
- Process of volcanic eruption
- Volcanic ash
- Volcanic ash
- Volcanic landform
- Volcanic ash
- Volcanic ash
- Volcanic and plutonic rocks difference
- Volcanic cinder appraisal
- Tephra
- Cinder cone volcano
- Volcanic ash
- Volcanic landform
- Volcanic landform
- Arches national park geology
- Volcanic ash
- A whalebone that originally contained 200 grams
- Volcanic ash
- Volcanic landform
- Volcanic ash
- Volcanic hazards
- Define folding faulting and volcanic activity
- Volcanic island arc
- Volcanic ash
- Tambora eruption
- Sigmet volcanic ash
- Batholith
- Types of volcanoes
- Volcanic belts form along the boundaries of earth's
- Tectonic playe map
- Volcanic ash
- Whittaker
- Volcanic ash
- Volcanic ash
- Volcanic ash
- Volcanic ash
- Volcanic ash
- Volcanic ash
- Volcanic landform
- Volcanic features
- Divergent plate boundary
- Volcanic ash
- Volcanic ash
- Volcanic island arc map
- Factor affecting volcanic eruption
- Volcanic ash
- Volcanic ash
- Volcanic ash
- Cinder cone
- Volcanic ash
- Volcanic landforms diagram
- Hard rock
- Volcanic ash
- Steps of secondary succession
- Tư thế ngồi viết
- ưu thế lai là gì
- Thẻ vin
- Cái miệng bé xinh thế chỉ nói điều hay thôi
- Thơ thất ngôn tứ tuyệt đường luật
- Các châu lục và đại dương trên thế giới
- Từ ngữ thể hiện lòng nhân hậu
- Diễn thế sinh thái là
- Thứ tự các dấu thăng giáng ở hóa biểu
- Phép trừ bù
- Alleluia hat len nguoi oi
- Tỉ lệ cơ thể trẻ em
- Sự nuôi và dạy con của hươu
- đại từ thay thế
- Vẽ hình chiếu vuông góc của vật thể sau