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SUPP EXAM
KIGALI INSTITUTE OF SCIENCE AND TECHNOLOGY
Avenue de l'Armée,
B.P. 3900 Kigali,
Rwanda
INSTITUTE EXAMINATIONS -SEM:II
ACADEMIC YEAR 2012-2013
FACULTY OF ENGINEERING
DEPARTMENT: CIVIL
ENGINEERING & ENVIRONMENTAL TECHNOLOGY
II
SEMESTER:
MODULE:
CEE 3222 ENGINEERING GEOLOGY
DATE:
GROUP:
CE and WEE
YEAR: II
/ 04 /2013
TIME:
2hours
MAXIMUM MARKS =
60
INSTRUCTIONS
1. This paper contains FOUR (4) questions.
2. Answer THREE (3) Questions only:
Question ONE (1) from Section “A” is Compulsory and Answer any TWO (2) from
Section “B”
3. All questions carry equal marks.
4. No written materials allowed.
5. Do not forget to write your Registration Number.
6. Write all your answers in the booklet provided
7. Do not write any answers on this questions paper.
8. Start each question in a NEW page
SECTION: A
Question: 1
[20]
a. Complete the following table with some mineral properties
[12]
Minerals present in the 4 main groups of igneous rocks
Rock
Composition
Acid
Amount
of
SiO2/%
(1)
Syenites, Granites
(2)
(3)
55-65
(4)
Plagioclase,biotite,hornblende,quartz,orthoclase,(au
gite)
Basic
(5)
Gabro
(7)
45
(8)
Rocks
Mineral
(6)
Ca-plagioclase, Olivine,(Augite)
b. Define with schematic view the phenomenon of unconformity
[8]
SECTION: B
Question: 2
Define the following terms which are used for describing igneous rock texture [20]
-
Holocrystalline
[2]
-
Hypocrystalline
[2]
-
Hyalocrystalline [2]
-
Phaneritic
[2]
-
Aphanitic
[2]
-
Glassy
[2]
-
Equigranular
[2]
-
Lnequigranular
[2]
-
Porphyritic
[2]
-
Euhedral
[2]
Question: 3
The intensity of an earthquake can be estimated by using two methods recognized
internationally.
a. What are these two methods?
b. Define and explain every method in details
Delete part (c) because (b) composes even the difference between them
[20]
[2]
[18]
Question: 4
[20]
a. Explain in details the mechanical and chemical processes which affect the earth’s surface
[10]
b. Explain using schematic view the process of hydrological cycle
[10]
MARKING SCHEME
Question: 1
(a). (1): 65%[1]
(2):
Quartz, Orthoclase, Na-plagioclase, Muscovite, biotite, (Hornblende) [2]
(3) : Intermediate [1]
(4) : Granodiorite, diorite [1]
(5) : 45-55%[1]
(6) : Ca-plagioclase, Augite, (Olivine ; Hornblende)[2]
(7) :Ultra basic[1]
(8): Peridotites, Dunites [1]
(b).
[5]
[5]
Question: 2
Holocrystalline : entirely composed of crystals (cooled slowly [2]
Hypocrystalline : composed of crystals and glass[2]
Hyalocrystalline :no crystals, i.e. glassy (cooled quickly[2]
Phaneritic : individual crystals can be distinguished (cooled slowly[2]
Aphanitic : granularity from the presence of crystals can be seen, but individual crystals
cannot be distinguished[2]
Glassy : entirely glass-like, or some crystals set in glass (cooled quickly[2]
Equigranular : all crystals are approximately of equal size[2]
lnequigranular : some crystals are clearly larger than others[2]
Porphyritic : large crystals surrounded by much smaller crystals[2]
Euhedral: well defined regular shape (crystallized early from melt) [2]
Question: 3
a. Richter method and Mercalli method [2]
b. All earthquakes are generated in the outer 700 km of the Earth (Fig. 1.3) and all destructive
earthquakes, wherever they occur, originate at depths less than 70 km.
The intensity of an earthquake can be estimated from the effects felt or seen by an observer,
and such observations are collected and used to determine the Centre of the disturbance. They
are graded according to a Scale of Intensity such as the Mercalli Scale, which has twelve
grades: [4]
[6]
[6]
C. The difference between the two methods is that, Mercalli’s scare concern Macro seism and
Richter scale concern Micro seism.[2]
Question: 4
a. External processes include weathering: the disintegration and decomposition of rock at or
near Earth’s surface; mass wasting: the transfer of rock material down slope under the
influence of gravity; and; erosion: the removal of material by a mobile agent, usually water,
wind, or ice. They are called external processes because they occur at or near Earth’s surface
and are powered by energy from the Sun. By contrast, internal processes, such as volcanism
and mountain building, derive their energy from Earth’s interior.[3]
Mechanical weathering is the physical breaking up of rock in to smaller pieces. Rocks can be
broken into smaller fragments by frost wedging (where water works its way into cracks or voids
in rock and upon freezing expands and enlarges the openings), salt crystal growth, unloading
(expansion and breaking due to a great reduction in pressure when the overlying rock is eroded
away),and biological activity (by humans, burrowing animals, plant roots, etc.).[3]
Chemical weathering alters a rock’s chemistry, changing it in to different substances. Water
is by far the most important agent of chemical weathering. Oxygen dissolved in water will
oxidize iron-rich minerals, while carbon dioxide (CO2) dissolved in water forms carbonic acid,
which attacks and alters rock.
The chemical weathering of silicate minerals frequently produces soluble products containing
sodium, calcium, potassium, and magnesium ions, as well as silica in solution; insoluble iron
oxides, including limonite and hematite; and clay minerals.
The rate at which rock weathers depends on such factors as particle size : small pieces
generally weather faster than large pieces; mineral make-up: calcite readily dissolves in
mildly acidic solutions, and silicate minerals that form first from magma are least resistant to
chemical weathering; and climatic factors: particularly temperature and moisture. Frequently,
rocks exposed at Earth’s surface do not weather at the same rate. This differential weathering
of rocks is influenced by such factors as mineral make-up and degree of jointing.[4]
b. Ground-water is the fluid most commonly encountered in engineering construction. It is
derived from many sources but most now comes from rainfall and melting snow and is termed
meteoric ground-water. The passage of water through the surface of the ground is called
infiltration and its downward movement to the saturated zone at depth is described as
percolation. Water in the zone of saturated ground moves towards rivers, lakes and the seas, a
process known as ground-water flow, where it is evaporated and returned to the land as clouds
of water vapour which may precipitate as rain or snow.
Thus a cycle of events exists, namely precipitation on land, infiltration and percolation, groundwater flow to open water, evaporation and thence precipitation, so starting another cycle. This
circulation of water is termed the hydrological cycle (Fig. 13.1). The seas and oceans contain
approximately 97% of all the water presently involved in the cycle, a little more than 2% is in
the form of snow and ice and less than 0.1% is water vapor. The remaining0.9% is distributed
in lakes, rivers and ground-water. [5]
[5]