Introduction to the Earth Basic Terminology and Concepts

Introduction to the Earth Basic Terminology and Concepts Spring 2012 , Lecture 1

Ecosphere • That part of the earth consisting of the atmosphere, hydrosphere, lithosphere, and biosphere 2

Atmosphere • The gaseous layer which surrounds the earth, and which is held by gravitational attraction. It consists of layers, the bottom ones of which are: § § § § Thermosphere > 80 km Mesopause Mesosphere 45 - 80 km Stratopause Stratosphere 12 - 45 km Tropopause Troposphere 0 -12 km 3

Hydrosphere • Earth's water, in any physical state – § Gaseous § Liquid § Solid 4

Lithosphere • The outermost part of the solid earth, consisting of the entire crust and the upper mantle, from the surface to a depth of about 70 kilometers (km) • It is stronger and mechanically more rigid than the asthenosphere (70 - 250 km), which lies under it 5

Interior of the Earth • Crust – § Continental (0 -40 km, to a maximum of 100 km) § Oceanic (0 -10 km) • Mantle – § Upper (bottom of crust to 700 km, and includes the transition zone (350 to 700 km) § Lower (700 - 2900 km) • Core – § Outer (2900 - 4980 km - liquid iron-nickel) § Inner (4980 - 6370 km - solid) 6

Biosphere • Interface layer between earth's crust, atmosphere, and hydrosphere where life is found • Includes the total ecosystem of the earth 7

Ecosystem • Community of interacting organisms, of all species • Includes interactions of this community with the chemical and physical systems of earth 8

Human Activities • Interact with the natural world, causing changes in the ecosystem • Changes vary in magnitude and temporal scale 9

Environmental Issues • Changes in the ecosphere caused by: § Natural processes § Human activities • Often cause change • Affect the rate at which change occurs • Or both 10

Changes By Other Species • Humans are not the only species to cause environmental change • Cyanobacteria, the first organisms capable of photosynthesis, gradually changed the atmosphere of earth from one without oxygen to one with the present 21% oxygen content 11

So What Makes Humans Different? • Humans are the first species to be aware of their influence • Humans assume, to some extent, responsibility for wise management of the planet • Humans affect change at rates unprecedented in the geological record 12

Technology Improvements • During the last fifty years • Have greatly contributed to our awareness of environmental change § Especially contributing to our knowledge of global scale processes • Greatly enhanced out knowledge of the temporal scale of global change 13

Examples of Technological Change • Satellite observations • Computational power • Rapid communication (Internet) 14

Changes to the Ecosphere • Many examples of modification of ecospheric components have been described • Representative examples of these modifications are shown on the following slides 15

Atmospheric Modifications • Depletion of ozone (O 3) in the ozone layer (stratosphere) which affects UV light absorption § Ozone “hole” § Leads to increased rates of skin cancer • Acid deposition – introduction of pollutant gasses into the atmosphere leads to the formation of “acid rain” 16

Atmospheric Modifications cont. • Modification of the climate system by the introduction of “greenhouse” gases § Major gases are carbon dioxide, freons, methane, nitrous oxide § Are leading to a warmer earth, and will increase number and severity of major storms § May affect short and medium term climate, and may modify the areas in which food can be grown § May create climate refugees 17

Hydrological Modifications • Diagram shows a local example of the hydrological cycle 18

Hydrological Cycle Modifications • • Withdrawal of water Pollution of water Impoundment of water (dams) Modifications in erosion and depositional rates § Silting of rivers and estuaries § Increased erosion below dams § Changes in form of precipitation – rain rather than snow 19

Biosphere Modifications • Mobilization and redistribution of chemical elements • Most important carbon (C), nitrogen (N), and oxygen (O) § Results in enrichment and depletion of various parts of the system, leading to problems like red tide, depletion of soil productivty, etc. 20

Biosphere Modifications cont. • Human activities change natural environment § Often results in changes in species distribution, especially in loss of biological diversity (biodiversity) § Rapid expansion of urban and suburban areas decreases available habitat § Deforestation § Expansion of farming into marginal environments § Land use that is insensitive to long term changes • Salinization 21

Results of Environmental Change • Species reduction § Mass mortality - a large number of individuals die, which may lead to a new equilibrium distribution, with a smaller number of individuals of the species in question, or the original equilibrium may be approximately restored, to precatastrophe levels § Extinction - A complete elimination of a species. Extinction can and does occur naturally - Man's activities have increased the rate of extinction 22

Natural Events • Natural events often lead to mass mortality in many species - extinction may occur in severely geographically restricted species • Examples: § § § Earthquakes Volcanoes Tsunamis Hurricanes Small meteorite impacts 23

Large Scale Extinction • Large meteorite impacts can result in mass extinctions § Example: Cretaceous-Tertiary event that wiped dinosaurs, and many other species, from the face of the earth • Large scale nuclear would probably have the same effect 24

Environmental Action • Awareness of environmental change does not always translate to actions favorable to the stabilization of the ecosystem • Why? 25

Political Problems • Politicians make most policy decisions, yet relatively few politicians have any training in science or technology § Some overcome this by relying on science/technology advisors • Political considerations may cause them to rely more heavily on political or economic advisories, whose perspective is usually focused on a much smaller time scale 26

Economic Gain • Short term economic gain is a powerful motive • Example: Drilling for oil in the Arctic Wildlife Preserve will provide profit, and will very temporarily stave off the decline in oil production § This may make the final decrease in petroleum even more difficult for humans, since we will have built more automobiles, power plants, etc. § It will also create immense difficulties for many Arctic species 27

Sources of Pollution • Pollution may occur from a variety of sources • Generally we can divide pollution sources into two types: § Point sources – pollution emanating from a single source, such as a power plant smokestack § Non-point sources – pollution derived from a variety of sources, such as smog from automobile exhaust 28

Scope of Environmental Problems • Environmental problems are generally split into one of three groups, with the possibility of overlap between groups § Local – effluent introduced into a stream from an industrial plant § Regional – acid rain in the northeastern U. S. , extending into Canada § Global – Greenhouse gas warming of the planet 29