lecture 4 - geology
TRANSCRIPT
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 1/10
Earthquakes,Folds, Fractures in
Rocks, Mass Wasting, KarsticPhenomena.
Course 4
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 2/10
How the Earth-crust¶s was made
Geomorphology- study the landsforms and their modifications thanks to
intrusive or extrusive factors
The landsforms can be:
- As first order (planetary)
- the biggest landsforms of the crust - the continentals blocks
- the oceanic basins
-As second order (major landsforms)- units from oceanic basins and of continents
- they are made by intrusive factors
- contain - orogenical zones - with curly layers (the mountains, the hills)
- platphorms zones - with horizontal layers (the tablelands, the
plains)
-As third order (micro-relief)- small landsforms
- they are the result of extrusive factors
- they can be erosive, acumulation or tectonics forms
The intrusive factors - the internal dynamic ( the tectonics plates movement)
The extrusive factors - the external dynamic ( the atmosphere, hydrosphere
actions)- weathering
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 3/10
THE INTERNAL DYNAMIC
Contain:
-the orogenic motions (horizontal) - the earthquakes
- the epirogenic motions (vertical) - the volcanism- the tectonics plates motions - the gravity
OROGENICAL MOTIONS ± the effect is an important deformation of layers
Hinge line
Limb
Hinge plane
folds¶ angle
Folds type:
-Vertical -Recumbent
-Bending - overturned
The folds µ elements are:
Obs. Salt folds
Isoclinal folds
Anticlinal folds
Mountains chains
Obs. When the deformation keep the continuity of rocks, appear the FOLDS
folds¶ shaft
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 4/10
- The fault¶s flanks(A and B)
-the fault¶s plan (P)
-the fault¶s direction
-the fault¶s step (jump) (p)
The Volcanism- is tying to ridge zone and to subduction zone of tectonics plates
The magma from astenosphere arrive to the surface, by a volcano
The volcano components parts are:
-the crater
-the cone
-the feeders
-the magma chamber
piroclastic and igneous rocks
A
BP
The fault elements are:
p
THE FRACTURING= FAULT- are break in the Earth-crust which suffer change of
place
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 5/10
EARTHQUAKES (SEISMICAL MOTIONS)
Definition Earthquake is a trembling, a shaking of a ground caused by the
sudden release of energy stored in the rocks beneath the Earth¶s surface
The earthquake elements are:-The length- second fractions, rarely few seconds
-The intensity- is a measure of an earthquake¶s effect on people and building
- micro-quake ±measured with a seismograph
- macro-quake- they are felt by people
-The frequency- every year almost 100000 earthquakes ( quake each 5minutes)
-The depth- the distance from hypocenter (in deep) to epicenter (to surface)
-Quakes are classified into three groups according to their depth of focus, as:
-shallow focus 0 - 70 km deep - 85%
-intermediate focus 50-70 ± 350 km deep -12%
-deep focus 350 ± 700 km deep 3%The point on the earth¶s surface
directly above the focus is the epicenter
Seismic waves±longitudinally (7-13 km/s), transversally (4-7 km/s),
and superficially (3-3,5 km/s)
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 6/10
THE EARTHQUAKE¶S CAUSES
Cosmic causes- due to falling of cosmic bodies on the Earth¶s surface
Ex: meteorites
Earth¶s cause- volcanic quakes explosions- are local, depending of volcaniceruptions (represent 10% of earthquakes)
- breakdown quakes- the breakdown of natural caves roof of
earth¶s crust Ex. In limestone caves; in salt, in gypsum due to underground
explosion
- tectonic quakes-due to subduction of tectonic plates (80% of
all earthquakes)
Quakes intensity are expressed in Mercalli scale
Richter scale is a numerical scale of magnitudes
Richter
Scale
Mercalli
Scale
2 3 4 5 6 7 8 9
1,5 3 4,5 6 7,5 9 10,5 12
Earthquakes from Romania ± Vrancea zone, tranyilvania zone (Mures-Tarnave),
Banat zone (Periam-Vinga), Fagaras zone (at S of Fagaras Mountains),
Sea zone (Constanta-Mangalia), Danube zone (Moldova Noua- Virset)
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 7/10
GEODYNAMIC PROCESS REGARDING THE BUILDING ACTIVITY.
MASS WASTING
Because of the force of gravity the various agents of erosion (moving
water, ice and wind) work to make slopes gentler and therefore increasinglymore stable
1. FALL- accurs when material free-falls or bounces
down a cliff
2. LANDSLIDES- slow-to-very-rapid descent of rock
or soil
1. Detach surface2. Slides terrace
3. Transversally crack
4. Longitudinally crack
5. Slide¶s surface
6. Slide¶s foot
7. Slide¶s base
The landscape¶s elements are:
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 8/10
TYPE OF LANDSLIDES MOVEMENT:
Flow- the descending mass is moving
downslope as a viscous fluid ( 1a)
Slip- the descending mass remains
relatively coherent moviung along one
ore more well-defined surfaces (1b)
Slump - movement along a curved surfacethe upper part moving downward while
the lower part moves outward
While the slides are producing on the ground mass, two forces are acting:
-The passive force- (strength force)- which holds this mass in stable equilibrium
(cohesion and internal friction of particles)
-The active force -(slides force)-which moves this mass (hydrodynamic
pressure, own weight)
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 9/10
THE LAYER¶S BEND EXTREMITY
-is due to the gravity
-the layer¶s extremity of rocks arebend in the same direction as the
slope side
-appear frequently in marly ±clays
and rarely in limestone
THE SETTLE ±it¶s a process of packed, due to own rock¶s weight or to
building¶s weight
SUPHOSION- is due to the soluble componentswhich are dissolved by ground water
Obs. The ground motions due to suphosion can
be control by drain
8/3/2019 Lecture 4 - Geology
http://slidepdf.com/reader/full/lecture-4-geology 10/10
SOLIFLUCTION ± is the flow of water- saturated debris over impermeable
material
-usually takes place in arctic or subarctic climates where the ground is
permanently frozen (permafrost)
KARST PHENOMENA- all the geological process which appear in soluble
rocks, specially in limestone, due to ground water circulation (water with CO2)
Soluble rocks- the salt, the gypsum, the anhydrite, the limestone and the
dolomiteKarts - to surface- natural bridges, key
-to interior- caves, underground channel