EARTH AS A SYSTEM

Anyone who studies Earth soon learns that our planet is a dynamic body with many separate but interacting parts of spheres.

All of these parts are related in some way to the others and form a complex and continuously interacting whole we call the Earth system.

Here is a practical example of the interactions among different parts of the Earth system: from the Atlantic Ocean (hydrosphere) moisture evaporates (into the atmosphere), falls as rain in the Alps (to the geosphere) triggering destructive debris flow in Log pod Mangartom (see EC17 - Destructive debris flow).

The Earth system has a nearly endless array of subsystems in which matter is recycled over and over again. There are many more or less familiar loops or subsystems:

- hydrologic cycle,

- rock cycle (see next page: Rock Cycle),

- carbon cycle...

These cycles are by no means independent of each other - they interface at many places and interact in various processes. We could name rock and hydrologic cycles as an example.

ENERGY FOR THE EARTH SYSTEM

The Earth system is powered by enegry from two sources. The Sun drives external processes that occur in the atmosphere, hydrosphere, and at Earth's surface. Water and climate, ocean circulation, and erosional processes such as rivers, glaciers, wind, and waves are driven by energy from the Sun.

Earth's interior is the second source of energy. Heat remaining from when our planet formed, and heat that is continuously generated by decay of radioactive elements, power the internal processes that produce volcanoes, earthquakes, Earth crust movement, and formation of mountains.

Slika 5.1: Plaz (zgornji del slike), pot drobirskega toka in uničen del vasi (spodnji del slike.
 / Figure 5.1: Landslide caused by extensive rain (top of photo), debris flow course, and destructed part of the village (bottom of photo).
Slika 5.2: Del Loga pod Mangartom,ki ga je uničil drobirski tok.
/ Figure 5.2: a part of the destruction in Log pod Mangartom village, caused by the debris flow.

SISTEM ZEMLJA

Pri preučevanju Zemlje hitro ugotovimo, da je naš planet dinamično telo z mnogo različnimi, a medsebojno odvisnimi sistemi. Vsak od teh delov je na tak ali drugačen način povezan z ostalimi ter tako tvori kompleksno, neprekinjeno povezano in delujočo celoto, ki jo lahko imenujemo kar Sistem Zemlja.

Naj navedem konkreten primer medsebojnega vplivanja različnih delov "Sistema Zemlja": iz Atlantskega oceana (hidrosfere) vlaga izhlapeva (v atmosfero), pade kot dež v Alpah (na geosfero) in sproži uničujoč drobirski tok v Logu pod Mangartom (glej tudi EC17 - Uničujoč drobirski tok ).

Sistem Zemlja ima skorajda neskončno množico podsistemov v katerih se snovi reciklirajo, oziroma znova in znova krožijo. Nekaj od teh krožnih podsistemov je kar splošno poznanih:

- vodni (ali hidrološki) krog,

- kamninski krog (glej naslednjo stran "Kamninski krog"),

- ogljikov krog ali cikel...

Ti cikli med seboj nikakor niso neodvisni - med seboj se stikajo na mnogih mestih in medsebojno vplivajo v različnih procesih. Kot primer bi lahko navedli kamninski in vodni krog, ki sta zelo prepletena.

ENERGIJA ZA DELOVANJE "SISTEMA ZEMLJA"

"Sistem Zemlja" poganjata dva vira energije. Sonce poganja zunanje procese, ki se zgodijo v atmosferi, hidrosferi in na Zemeljski površini. Voda in vreme, kroženje v oceanih in erozijski procesi rek, ledenikov, vetra in valov so gnani z energijo Sonca.

Zemljina notranjost je drugi vir energije. Toplota preostala iz časa nastanka planeta in toplota, ki jo neprestano proizvaja razpadanje radioaktivnih elementov, poganjata notranje procese, ki povzročajo vulkansko dejavnost, potrese, premike plošč Zemljine skorje in njihovo "potovanje", nastajanje gorovij.