CHAPTER 2 ENERGY FLOWS IN EARTH HISTORY AND NATURAL DISASTERS

“Disasters occur where and when the Earth’s natural processes concentrate energy and then release it, killing life and causing destruction.” (p. 26) We are interested in these processes as: (1) Earth population growth forces individuals into regions of greater risk (2) media gives more real-time coverage to disasters

Earth processes are powered by four primary energy sources (1) Internal Earth heat – energy on continuous surface-ward migration … short-term is released through volcanoes, earthquakes, geysers, mudpots, etc … long-term this energy has powered movement of continents, and contributed to formation of the atmosphere and oceans

Earth processes, cont (1) Internal Earth heat, cont “atomic power”, largely counter-balanced by degradational forces (solar + gravity) reducing the Earth surface in conjunction with gravitational energy (heat- producing contraction of Earth materials) and impact energy (kinetic energy converted to heat energy), this radioactive energy altered internal Earth composition … significantly, across the time of the Earth, this radioactive energy has been in decline

Can we tell if events are related? If an earthquake happens at the time of a volcanic eruption, did the eruption cause the earthquake or did the earthquake cause the eruption – or are they coincidence?

Geologists studying the stirrings of Mt. St. Helens, Washington, in 1980 be its catastrophic eruption, monitored swarms of earthquakes and decided that most recorded the movement of rising magma as it squeezed upward, expanding the volcano.

What about the bigger earthquake at the instant the volcano erupted the morning of May 18 th ? The expanding bulge over the rising magma collapsed in a huge landslide. Certainly neither the landslide nor the earthquake caused the formation of the molten magma.

Once formed, neither caused the magma to rise, but did they trigger the final eruption? If so, which one triggered the other – the earthquake, the landslide, or the eruption? Were the events directly related – that is, did one cause the others? And, what about the devastating debris flows that immediately followed?

Parkfield, CA Determining if hazardous events are related (and therefore can be modeled and predicted) is a major scientific goal For lithospheric disasters, seismologists and geologists have what they think is an advantage in the small town (18 inhabitants) of Parkfield, CA. Parkfield is unusual. Since the mid-1800s 7 magnitude-6 earthquakes have originated in its area, roughly every 22 yrs. The most recent occurred 09/28/04 Parkfield is a USGS monitoring station for the San Andreas Fault

Earth processes, cont (2) The sun – the fractional portion of insolation reaching the Earth’s surface powers the Hydrologic Cycle and powers convection and advection; the source of our degradational forces (wind; ice; water)… (text calls it our most important external energy source) … and powering atmospheric hazards (storms; flooding; lightning; etc)

Earth processes, cont (3) Impact of extraterrestrial bodies – asteroids and comets arriving from outer space; [Interesting: Text calls them “visitors”] abundant and important early in Earth history – minor collisions remain frequent; significant events are infrequent, but can be catastrophic and global in extent

Earth processes, cont (4) Gravity – “gravity is the immediate force that drives agents of erosion” attraction between objects, a factor correlated to the product of their masses and inversely proportional to the distance between them; text relates that at equal distance, the greater the mass of the bodies the greater the gravitational attraction; as the text relates, it is a force that humans are unable to modify

Earth processes, cont all objects with mass create gravitational attraction (even us) became a factor as the Earth became increasingly dense during its first million yrs; denser materials drawn downward to the Earth’s Core: (1) accelerating gravitational force: (2) constant supply of molten material (3) created internal Earth strata by density

Earth processes, cont gravitational differences separated materials into current concentric zonation inner core outer core mantle crust Earth-Sun-Moon gravitational conflict results in tidal energy gravitational force on the Earth surface dictates movement of water; ice; mass movement