Prof.Dr.Kadir DİRİK Lecture Notes

2015

GEOLOGY FOR MINING ENGINEERS

Most of the Earth is solid rock, surrounded by the hydrosphere, the biosphere, and the atmosphere. Prof.Dr.Kadir Dirik Lecture Notes

GEOLOGY is the study of the Earth, including the materials that it ismade of, the physical and chemical changes that occur on its surfaceand in its interior, and the history of the planet and its life forms.

THE SCIENCE OF GEOLOGY

Prof.Dr.Kadir Dirik Lecture Notes

The hydrosphere includes water in streams, wetlands, lakes, and oceans; in the atmosphere; and frozen in glaciers. It also includes ground water present in soil and rock to a depth of at least 2 kilometers.

The atmosphere is a mixture of gases, mostly nitrogen and oxygen. It is heldto the Earth by gravity and thins rapidly with altitude. Ninety‐nine percent isconcentrated within 30 kilometers of the Earth’s surface, but a few tracesremain even 10,000 kilometers above the surface.

The biosphere is the thin zone near the Earth’s surface that is inhabited bylife. It includes the uppermost solid Earth, the hydrosphere, and the lowerparts of the atmosphere. Land plants grow on the Earth’s surface, with rootspenetrating at most a few meters into soil.Animals live on the surface, fly a kilometer or two above it, or burrow a fewmeters underground. Sea life also concentrates near the ocean surface,where sunlight is available. Some aquatic communities live on the deep seafloor, bacteria live in rock to depths of a few kilometers, and a fewwindblown micro organisms are found at heights of 10 kilometers or more.But even at these extremes, the biosphere is a very thin layer at the Earth’ssurface.

Prof.Dr.Kadir Dirik Lecture Notes

Most of the Earth is composed of rocks. Rocks, in turn, are composedof minerals

Prof.Dr.Kadir Dirik Lecture Notes

Most of the Earth is solid rock, surrounded by the hydrosphere, thebiosphere, and the atmosphere. Although more than 3500 different mineralsexist, fewer than a dozen are common. We study the origins, properties, andcompositions of both rocks and minerals.

There are two processes acting on the earth namely internal and externalprocesses

INTERNAL PROCESSESProcesses that originate deep in the Earth’s interior are called internalprocesses. These are the driving forces that raise mountains, causeearthquakes, and produce volcanic eruptions.

SURFACE PROCESSESSurface processes are all of those processes that sculpt the Earth’s surface.Most surface processes are driven by water, although wind, ice, and gravityare also significant.

Prof.Dr.Kadir Dirik Lecture Notes

UNIFORMITARIANISM AND CATASTROPHISM

James Hutton was a gentleman farmer who lived in Scotland in the late1700s. Although trained as a physician, he never practiced medicine and,instead, turned to geology. Hutton observed that a certain type of rock, calledsandstone, is composed of sand grains cemented together. He also noted thatrocks slowly decompose into sand, and that streams carry sand into thelowlands. He inferred that sandstone is composed of sand grains thatoriginated by the erosion of ancient cliffs and mountains.

Hutton’s conclusions led him to formulate a principle now known asuniformitarianism. The principle states that geologic change occurs over longperiods of time, by a sequence of almost imperceptible events. Huttonsurmised that geologic processes operating today also operated in the past.Thus, scientists can explain events that occurred in the past by observingchanges occurring today. Sometimes this idea is summarized in the statement“The present is the key to the past.”

Prof.Dr.Kadir Dirik Lecture Notes

William Whewell, another early geologist, agreed that the Earth is very old, but heargued that geologic change was sometimes rapid. He wrote that the geologic past mayhave “consisted of epochs of paroxysmal and catastrophic action, interposed betweenperiods of comparative tranquility.” Whewell was unable to give examples of suchcatastrophes. He argued that they happen so infrequently that none had occurredwithin human history.Today, we know that both Hutton’s uniformitarianism and Whewell’s catastrophism arecorrect. Thus, over the great expanses of geologic time, slow, uniform processes aresignificant, but improbable, catastrophic events radically modify the path of slowchange.Gradual Change in Earth HistoryWithin the past few decades, geologists have learned that continents creep across the Earth’s surface at a rate of a few centimeters every year.Catastrophic Change in Earth HistoryChances are small that the river flowing through your city will flood this spring, but ifyou lived to be 100 years old, you would probably see a catastrophic flood. When westudy the 4.6 billion years of Earth history, they find abundant evidence of catastrophicevents that are highly improbable in a human lifetime or even in human history. Forexample, giant meteorites have smashed into our planet, vaporizing enormous volumesof rock and spreading dense dust clouds over the sky. Similarly, huge volcanic eruptionshave changed conditions for life across the globe. Geologists have suggested that thesecatastrophic events have driven millions of species into extinction.Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes

THE GEOLOGIC TIME SCALEGeologists have divided Earth history into units displayed in the geologic time scale. The units are called eons, eras, periods, and epochs and are identified primarily by the types of life that existed at the various times.

Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes

The Origin of the Solar System and the Differentiation of the Early Earth

The currently accepted theory for the origin of our solar system involves: (a) a hugenebula condensing under its own gravitational attraction, then (b) contracting, rotating, and (c) flattening into a disk, with the Sun forming in the center and eddiesgathering up material to form planets. As the sun contracted and began to visiblyshine, (d) intense solar radiation blew away unaccreted gas and dust until finally,  (e) the Sun began burning hydrogen and the planets completed their formation.  

Heat from the Sun boiled most of the hydrogen, helium, and other light elements away from the inner Solar System. As a result, the four planets closest to the Sun—Mercury, Venus, Earth, and Mars—are now mainly rocky with metallic centers. These four are called the terrestrial planets because they are “Earthlike.” In contrast, the four outer planets—Jupiter, Saturn, Uranus, and Neptune—are called the Jovian planets and are composed primarily of liquids and gases with small rocky and metallic cores.

(a) Mercury is a small planet close to the Sun. Consequently, most of the lighter elements have long since been boiled off into space, and today the surface is solid and rocky. (b) Jupiter, on the other hand, is composed mainly of gases and liquids, with a small solid core.Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes

(a) The early Earth was probably of uniformComposition and density throughout, (b) Heating of the early Earth reached the melting point of iron and nickel, which, beingdenser than silicate minerals, settled to the Earh’s center. At the same time, the lightersilicates flowed upward to form the mantleand the crust.(c) In this way, a differentiated Earth formed, consisting of a dense iron‐nickel core, an iron‐rich silicate mantle, and a silicate crust with continents and ocean basin

A schematic view of the interior of the Earth

Jumps in density between Earth’s major layers caused by changes in their chemicalcomposition Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes

Continents float high because they are made of rocks with lower densities than rocksof the mantle or oceanic crust

Prof.Dr.Kadir Dirik Lecture Notes

Axial ridgeGivergent boundary Transform

Subduction zoneConvergent boundary Extensional zone in the continents Uncertain plate boundary

Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes18

(Monroe&Wicander, 2005)

Continentallithosphere

Trench

Mid‐oceanic ridgeOcean

SubductionOceaniclithosphere

Convection carries heat upward by the motion of matter

An idealized cross section illustrating the relationship between lithosphere and underlyingasthenosphere and the three principal types of boundaries convergent (yaklaşan), divergent(uzaklaşan) and transform (transform).

Prof.Dr.Kadir Dirik Lecture Notes19

(Monroe&Wicander, 2005)

Transformplate boundary

Mid‐oceanic ridge

Divergentplate boundary

Upwelling

Continental‐Continentalconvergentplate boundary

Continental‐Oceanicconvergentplate boundary

Trench

Divergentplate boundary

Upwelling

Oceanic‐Oceanicconvergentplateboundary

Asthenosphere

Lithosphere

Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes

Prof.Dr.Kadir Dirik Lecture Notes