Electronic Material Properties - und Geowissenschaften ...

Institute of Applied
Geosiences
Physical Geology and Global
Cycles
In the solar system, Earth is an unique rocky planet with an ocean and an
atmosphere. It is inhabited by bacteria since about 4 billion years and by higher life -
plants and animals - since ca. 600 million years. Organisms, air, water, and rocks are
interconnected in an unending cycle of matter and energy: The Earth System.
The crustal plates of Earth are driven by radioactive heat. This causes creation of
new crust at mid-ocean ridges at rates of several centimetres per year. On the other
side, plate margins collide, become subducted into the mantle again, or fold up vast
mountain ranges like the Alps and the Himalayas, combining rocks of very different
origin. During subduction the basaltic crust is partially melted generating more felsic
magmas which rise to form continental-type plutons and to cause lines of andesitic
volcanoes such as occurring around the entire Pacific rim. This is called the
endogenic cycle of rocks.
At the same time Earth receives solar radiation which moves air and water in gigantic
cycles around the planet. Specifically the water cycle causes the denudation of
mountains by mechanical erosion and the leveling of plains by chemical weathering,
the latter aided tremendously by vegetation and their CO2-input to soils. This is called
the exogenic cycle of rocks.
This exogenic cycle is increasingly impacted by mankind. The radiation balance of
the atmosphere has been upset by the emission of carbon dioxide, methane and
other tracegases, Earth is warming. Industrially produced chlorinated hydrocarbons
have risen to the stratosphere, threatening the protective ozone layer. Dust from
traffic, industry and agriculture produce reagents which alter the air chemistry,
causing unprecedented interactions with the marine realm, with vegetation and even
with rocks through acidification, excessive deposition of nutrients and salts. Dry and
wet deposition of anthropogenic (i.e. produced by humans) particles can be
measured world-wide. The population explosion caused the intensification of
agriculture and the alarming loss of topsoil and cuts down on the extent of natural
ecosystems at the same time. The artificial fertilization of soils causes wide-spread
nitrate pollution of shallow ground waters and urbanization alters the water cycle
above and below ground. Local leakage and accidents with chemicals impact soil,
rivers and ground water. Civil engineering, discharges and denudation cause
alterations in almost all rivers world-wide and even coastal seas show increasing
eutrophication, siltation and ecosystem changes in the water column and in the
shallow sediments. The scars left by the mining of minerals and fossil energy are
visible everywhere and cause increasingly problems. Everywhere man has changed
the rate of natural processes. He spreads ever further into the landscape, utilizing
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