King Salaman UNIVERSITY
Faculty of Science
Subject: physical geology (year 1)
Lecturer : Ass. Prof. Dr. Mohamed Tawfik
Writing questions
31-12-2022
Write on:
1. Mechanical weathering
When a rock undergoes mechanical weathering, it is broken into smaller and smaller pieces, each
retaining the characteristics of the original material. The end result is many small pieces from a
single large one.
The breaking a rock into smaller pieces increases the surface area available for chemical attack. By
breaking rocks into smaller pieces, mechanical weathering increases the amount of surface area
available for chemical weathering. In nature, four important physical processes lead to the
fragmentation of rock: frost wedging, salt crystal growth, sheeting, and biological activity
A) Frost wedging: After water works its way into the cracks in rock, the freezing water enlarges the
cracks, and angular fragments eventually break off.
B) Salt crystal growth: Another expansive force that can split rocks is created by the growth of salt
crystals. Rocky shorelines and arid regions are common settings for this process. It begins when
sea spray from breaking waves or salty groundwater penetrates crevices and pore spaces in rock.
As this water evaporates, salt crystals form. As these crystals gradually grow larger, they weaken
the rock by pushing apart the surrounding grains or enlarging tiny cracks.
C) Sheeting: When large masses of igneous rock, particularly granite, are exposed at Earth’s surface
by erosion, concentric slabs begin to break loose. The process that generates these onion-like
layers is called sheeting. It takes place, at least in part, due to the great reduction in pressure
that occurs as the overlying rock is eroded away, a process called unloading.
D) Biological activity: Weathering can be accomplished by the activities of organisms, including
plants, burrowing animals, and humans. Plant roots in search of nutrients and water grow into
fractures, and as the roots grow, they wedge apart the rock. Burrowing animals further break
down rock by moving fresh material to the surface, where physical and chemical processes can
more effectively attack it. Decaying organisms also produce acids that contribute to chemical
weathering. Where rock has been blasted in search of minerals or for road construction, the
impact of humans is particularly noticeable.
2. Massive intrusive igneous activity
It consists of many features such as:
A pluton is a body of magma or igneous rock that crystallized at considerable depth within the crust.
Where plutons are exposed at the Earth’s surface, they are a distinguished by size.
Batholiths By far the largest intrusive igneous bodies are batholiths. Batholiths occur as mammoth
linear structures several hundred kilometers long and up to 100 Km2 wide.
Stock A smaller pluton that has a surface exposure of less than 100 Km2 wide.
Diapirs large blobs of magma worked their way upward through the lower crust and collected 5 to
30 kilometers below the surface, where they solidified, they called diapirs.
laccolith. When viscous magma intrudes between two layers of sedimentary rock, it may generate
enough pressure to lift the overlying layer into an arch. The magma then cools to form concordant,
mushroom-shaped or domed pluton
Writing questions 11
A. Prof. Mohamed Tawfik
King Salman University
King Salaman UNIVERSITY
Faculty of Science
Subject: physical geology (year 1)
Lecturer : Ass. Prof. Dr. Mohamed Tawfik
Writing questions
31-12-2022
3. Types of volcanos
Writing questions 11
A. Prof. Mohamed Tawfik
King Salman University
King Salaman UNIVERSITY
Faculty of Science
Subject: physical geology (year 1)
Lecturer : Ass. Prof. Dr. Mohamed Tawfik
Writing questions
31-12-2022
4. Major features of the ocean floor
If all water were drained from the ocean basins, a great variety of features would be seen, including
chains of volcanoes, deep canyons, plateaus, and large expanses of flat plains. In fact, the scenery
would be nearly as diverse as that on the continents. During the past 65 years, oceanographers have
used modern depth-sounding equipment and satellite technology to map significant portions of the
ocean floor. These studies have led them to identify three major regions: continental margins, deepocean basins, and oceanic (mid-ocean) ridges.
A. Continental Margins The continental margin is the portion of the seafloor adjacent to major
landmasses. It may include the continental shelf, the continental slope, and the continental rise.
a) continental shelf: the boundary between the continents and the ocean basins.
b) Continental slope: The boundary between the continents and the deep-ocean basins
c) Continental rise: In regions where trenches do not exist, the steep continental slope merges into a
more gradual incline known as the continental rise, a thick wedge of sediment that moved downslope
from the continental shelf and accumulated on the deep-ocean floor.
B. Deep-Ocean Basins Situated between the continental margins and oceanic ridges are deep-ocean
basins. Parts of these regions consist of incredibly flat features called abyssal plains.
C. Dotting the ocean floor are submerged volcanic structures called seamounts, which sometimes
form long, narrow chains.
D. Oceanic Ridges :The most prominent feature on the ocean floor is the oceanic ridge, or mid-ocean
ridge.
5. Earth system
The Earth system is a small part of the larger solar system, but it is very important to us. The Earth
system has its components, which can be thought of as its subsystems. These systems, or “spheres,”
are:
the atmosphere, the hydrosphere, the biosphere, and the geosphere. You, of course, are familiar
with the atmosphere, the gases that envelop the Earth.
The hydrosphere is the water on or near Earth’s surface. The hydrosphere includes the oceans, rivers,
lakes, and glaciers of the world. It also includes groundwater, which is water that lies beneath the
ground surface. Earth is unique among the planets in that two-thirds of its surface is covered by
oceans.
The biosphere is all of the living or once-living material on Earth.
The geosphere, or solid Earth system, is the rock and other inorganic Earth material that make up
the bulk of the planet.
Writing questions 11
A. Prof. Mohamed Tawfik
King Salman University