Unit 1: A Fragile System
Explain what density is & how it relates to stratification.
o Density = mass/volume; how much mass fits into a space. Unit: kg/m 3
o Stratification = less-dense materials float on top of denser materials
This is found in the atmosphere, the ocean, the earth, etc.
Explain why disaster scales are based on the Order-of-Magnitude concept, and interpret graphs with logarithmic
o Without using a log scale, sometimes a graph will be too large.
o “Orders of magnitude” are powers of 10 – a logarithmic graph steps by powers of 10
Converting an exponential curve into a logarithmic graph will give a linear graph.
o Many disaster scales use powers of 10: Richter, Fujita, Torino, Beaufort, etc.
Relate natural-disaster risk & intensity to frequency, return period, and consequences (costs).
o Risk = probability severity * cost of damage ($ + human lives)
o Intensity is inversely proportional to frequency.
o Return period = average number of years between disaster events of the same magnitude
RP (M) = time span of data / # of cases of magnitude M.
Explain how some recent disasters were associated with concentration or dilution of energy.
o Time scales for energy to build up and release
Concentration of energy Dilution of energy
Earthquakes: years -> minutes Tsunami: minutes -> hours
Volcanoes: decades -> days Floods: hours -> days
Hurricanes: months -> days
Storms: hours -> minutes
Rogue waves: hours -> seconds
Get the disaster info you need from reliable sources.
Compare tectonic, rock, hydrologic, and biogeochemical cycles.
o Involves the creation -> movement -> destruction of plates
o One cycle can last more than 200 million years!
o Types of plate boundaries
Divergent: two plates move away
Forms: large, underwater mid-ocean ridges
Rifts formed through seafloor spreading
Convergent: two plates collide
Subduction zone: one plate moves beneath another (usually ocean and continental)
At 100-120 km, melts and releases H2O and CO2 -> hot enough to cause lower crust to
melt -> magma moves up -> reaches surface -> erupts
Movement along a transform fault – most are beneath oceans but some are on continents
o Rock: aggregate of one or more minerals. Mineral: naturally occurring crystalline substance w/ specific
o Rock Cycle: recycling of three major groups of rock
Crystallization of molten rock -> igneous rock beneath/on Earth’s Surface
Weathering -> sediment Sediment is transported by wind/water/ice to depositional sites
Buried -> lithification -> sedimentary rock
Chemically active fluids + heat + pressure cause metamorphic rock to be formed
Eventually, temp high enough -> melt -> restart
o Cycling of water from oceans -> atmosphere -> continents -> back again
o Driven by solar energy
o Residence time: estimated avg time a drop of water spends in any part of the cycle
Only a tiny fraction of earth’s water is active at a certain time – often stored
Only ~.3% of all water important for life -> groundwater
o Cycling of an element/elements through atmosphere/lithosphere/hydrosphere/biosphere
Related to the other cycles
Tectonic provides water + gas, heat + energy. Rock and hydrological transfer and store.
Elements and chemicals are transferred via storage compartments/reservoirs
When a biogeochem cycle is understood, the rate of transfer (flux) among all components is known
List the 1st and 2nd most common elements in the earth, ocean, and atmosphere.
Elements Earth Crust Ocean Atmosphere