quiz I: disasters

chelyabinsk meteor

• small meteor traveling about 20x the speed of a bullet

• exploded in the stratosphere about 23km (15 mi) above the surface

• people there could feel the intense heat from the fireball as well as the shockwave from the explosion

• largest known meteor to enter the earth’s atmosphere since the tunguska event

tunguska event

• june 30, 1908 fireball exploded over tunguska river valley

• the blasting force equivalent of 10 megatons of TNT, 10 H-bombs

• 2,000 km of forest to be flattened and burned

• at least 1M heard the explosion

• estimated asteroid 20 to 50m in diameter

• missed a similar git in 2004 and could happen again

formation

1. 13.7 billion years ago: big bang

2. 13 billion years: formation of first stars (quasars)

• after 100,000 years quasars died

• death of quasars gave us the elements and scatters new elements into space

• H and He collected into what are called a solar nebula

3. 5 billion years ago: sun grew by buildup of matter from solar nebula

   • after formation of sun, other particles pushed away by solar wind and solar radiation

   • solar radiation and solar winds push unused material away from the newborn sun

   • as particles are pushed away, they’re differentiated by density

   • more dense material (rock and metals) closer to sun

   • lighter material (ice and gases) further from sun

   • particles become trapped in chaotic, unorganized rings around the sun they begin to grow, like dust bunnies into planets

   • rocky material in orbit around the massive sun, collected creating rocky planets (mercury, venus, earth, and mars)

   • gaseous material pushed away from the sun formed the gaseous planets (jupiter, saturn, uranus, and neptune)

4. 4.56 billion years ago: formation of the earth

• after formation of the planets, plenty of unused material left flying around

• periodic drama caused by the impact of material from outer space: asteroids, meteoroids, and comets

asteroids

• ranging in size from 10 (30ft) to 1000km (620 mi)

• most of these reside in asteroid belt between mars and jupiter

• composed:

  • rocky

  • metallic

meteroids

• ranging in size from dust size to 30ft

• meteoroids are broken up asteroids

• still in space

meteor

makes contact with our atmosphere

meteorite

• makes contact with surface

• chunks that fall to earth tell us about the composition of the parent bodies they came from

comets

• come in a variety of sizes

• composed of ice and gaseous material

• classic glowing tail or two

• originate in the Kuiper belt and Oort cloud

airbursts and impacts

• heat up due to friction as they fall through producing bright light and changing

• they will either explode into airburst or collude with earth as a meteorite (in Antarctica)

impact craters

• barringer crater in arizona

• bowl shaped depression w upraised rim

• rim is overlain by ejecta blanket, material blown out of the crater upon impact

• broken rocks cemented together into breccia

simple craters

• typically small less than 4 mi

• barringer crater

complex craters

• larger in diameter greater than 4 mi

• rim collapses more completely

• center uplifts following impact

why earth has so few impact craters

1. 70% of earth is covered in water

2. smaller meteors burn up in the atmosphere

3. eroded by natural processes

4. plate tectonics recycles crust

mass extinctions

• usually involves rapid climate change, triggered by:

  • plate tectonics

  • volcanic activity

  • impacts

• 5 major mass extinctions:

  • ordovician

  • late devonian

  • permian

  • triassic jurassic

  • cretaceous paleogene (K-Pg)

  • pleistocene

K-Pg

• dinosaurs disappeared along with many plants and animals

• luis alvarez and his son walter discovered that the clay contains an unusually high concentration of iridium

• yucatan peninsula

• 112 mi nearly circular as deep as 18 to 25 mi

inner core

• radius: 1220 km about the size of the moon

• material: solid, metallic

• made of: 90% iron with sulfur, oxygen, and nickel

outer core

• thickness: 2180 km

• material: liquid 10x denser than water

• made of: same composition as inner core

mantle

• thickness: 2900 km

• material: solid rocky

• made of: iron and magnesium silicates

oceanic crust

• more dense

• thinner

• younger

• basaltic

continental crust

• less dense

• thicker

• older

• granitic

kola borehole

• 40,200 ft to 12.2 km

• 19 years to drill

how we know about earth’s interior

• seismology

• seismic waves propagate through the earth

plate tectonics

• processes associated with the creation, destruction of “plates”

• earth’s crust is broken up into several dozen tectonic plates move around spread apart and collide

geologic processes

• govern the type, location, and intensity of natural processes and natural disasters

origin of plate tectonics

• alfred wegener (1880-1930) noticed similar shapes of continents and hypothesized they were once one giant landmass called urkontinent

• coined the continental drift in 1912

• sonar was invented lead to the discovery of mid-atlantic ocean ridge

paleomagnetism

refers to the magnetism of rocks and the intensity of the direction of magnetic field of earth in the geologic past

bathymetry

measure of ocean death

topography

mapping ocean floor

divergent

• spreading

• constructive

• ridge/rift

• volcanic activity and earthquakes

convergent

• subduction

• destructive

• trench

• volcanic activity

transform

• lateral sliding

• conservative

• no major effect

• no volcanic activity but earthquakes

• san andreas fault

oceanic oceanic

• older, denser oceanic crust subducts younger, less dense oceanic crust

• volcanic island arc, mountains, trenches

• tsunami, volcanic eruptions, and earthquakes

• ALeutian Island (Alaska)

continental oceanic

• dense oceanic crust subducts less dense continental crust

• volcanic island arc, mountains, trenches

• tsunami, volcanic eruptions, and earthquakes

• cascade mountain range

continental continental

• when continental crust collides with continental crust

• orogenies

• earthquakes

• Himalayas