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Earthquakes,Folds, Fractures in

Rocks, Mass Wasting, KarsticPhenomena.

Course 4

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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

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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

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- 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

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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)

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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)

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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:

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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)

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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

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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