This documents provides class notes for Geology, with the following topics: Earthquakes, Fossil fuel, Geology, History of the Earth, Igneous rocks, Mountain formation, Ore formation, Plate tectonics, Rocks and minerals, Volcanos
Geology
General
Earth science concerned with the solid Earth, the rocks of which it is
composed, and the processes by which they change over time
Geothermal gradient: the rate of increasing temperature with increasing
depth. The average is 3°C/100 meter, in Hungary, it is 6-8 °C/100 meter
because it is in a basin and there is thermal water
The internal structure of the Earth
Core
There are 2 different parts:
The inner core (solid)
composed of an iron and nickel alloy
the temperature is like that on the surface of the Sun and
it comes from the radioactive decay of uranium and thorium
Outer core (Fluid)
composed of iron and nickel
Mantle
Predominantly solid
Partly liquid (plastic)
Composed mainly of silicate rocks (SiO2 ->quartz and silicon)
Crust
Outermost layer
2 types
Continental crust
Thickness: 30-70 km
The upper layer is rich in silicon dioxole
The lower layer is rich in metals like iron and magnesium
Oceanic crust
Thickness: 7-11 km
,Lithosphere
The outermost layer of the Earth that contains the crust and the
uppermost solid part of the mantle
Asthenosphere
The plastic (Partly molten) part of the mantle right under the Lithosphere
The magnetism of the Earth
Magnetic field
It is the result of the motion of the solid inner core in the liquid outer
core
Magnetic the North and the South poles
Do not coincide with the geographical North and South poles
Plate tectonics
In general
Describes the motion of the plate of the Lithosphere
Lithosphere is made up plates, the plates move constantly because the
Earth is cooling inside to outside
Divergent plate boundary
It is an underwater moving
The magma rises from the Asthenosphere and it reaches the surface in a
central rift valley
The magma cools, solidifies so the edge of the plate is constantly building
The plates are pushed away from each other
The further we go the older part of the plate we reach
For example: Mid Atlantic Ridge, Africa Rift Valley
Convergent plate boundary
One plate sub ducts under the other and melt in the Asthenosphere
Oceanic plate and oceanic plate
An island arc appears
Also we can find an oceanic trench e.g. Marianna Trench, where is
appears
, Oceanic plate and continental plate
We can find an oceanic trench there
A folded mountain appears
E.g. South-America and Nazca plate
Continental plate and continental plate
A folded mountain e.g. Himalaya appears
It happens for example between the Eurasian plate and the Indo-
Austrian plate
Transform Boundary
It happens when 2 plates are slide next to each other
It is in the ocean basin and connects offsets in the mid-ocean ridges
It is a smaller number connect mid-oceanic ridges and subduction zones
E.g. St. Andreas Fault
Volcanoes/Volcanism
In general
Volcano: The place where magma reaches the surface
Magma: Molten rock material under the surface
Lava: Magma reaches the surface
Volcanic activity depends on the type of the plate boundary
Divergent plate boundary
Magma
Rises from the Asthenosphere
Contains low SiO2 , high Fe, Mg, Mn
The magma has a high temperature (~1000 °C), because of it it’s easily
flowing (=thin)
Type of volcano
Pillow lava
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