PHYSICAL GEOGRAPHY Notes - Way To NDA

 

 PHYSICAL GEOGRAPHY

Physical geography is an introduction to basic science principles in the fields of Geomorphology, Hydrology, Climatology, Pedology, Glaciology and Biogeography.

Systems and Models

• Systems have a structure that is defined by its parts and processes.

• Systems are generalizations of reality.

• Systems tend to work in the same way. This involves the inputs and outputs of material that is then processed causing it to change in some way.

• The various parts of a system have functional as well as structural relationships between each other.

• The fact that functional relationships exist between the parts suggests the flow and transfer of some type of energy and/or matter.

• Systems can be classified into Isolated System, Closed System, Open System, Morphological System, Cascading System, Process-Response System, Control System and Ecosystem.

• Within the boundary of a system we can find three kinds of properties.

➢ Elements – They are the kinds of parts that make up a system. These parts may be atoms or molecules, or large bodies of matter like sand grains, rain drops, plants, animals, etc.

➢ Attributes – Characteristics of the elements that may be perceived and measured.

➢ Relationships – Occurs between elements and attributes. These associations are based on cause and effect.

Energy and Matter

• Energy - Capacity to do work.

• Matter is the material (atoms and molecules) that constructs things on the Earth and in the Universe. Albert Einstein suggested early in this century that energy and matter are related to each other at the atomic level.

• Some forms of energy include heat, electricity, sound, energy of chemical reactions, magnetic attraction, energy of atomic reactions, and light.

• There are few types of energy which are as follows:

➢ Radiation– Emission of energy from a material object in the form of electromagnetic waves and photons.

➢ Chemical Energy- Energy produced or consumed in chemical reactions.

➢ Atomic Energy – Energy released from an atomic nucleus because of a change in its subatomic mass.

➢ Electrical Energy – Energy produced from the force between two objects having the physical property of electrical charge.

➢ Heat Energy– Energy created by the combined internal motion of atoms in a substance.

• In three ways energy can be transferred from one place to another: Conduction, Convection and Radiation.
• Matter is the material that makes up things in the Universe. All matter on the Earth is constructed of elements.
• The smallest particle that exhibits the unique chemical characteristics of an element is known as an atom.
• Atoms are composed of smaller particles known as protons, neutrons, and electrons.
• A proton is a subatomic particle that has significant mass and contributes a single positive electrical charge to an atom.
• Neutrons also have significant mass, but no electrical charge.
• Electrons are extremely light subatomic particles having a mass that is 1/1840 of a proton.
• Atomic mass number is an atom’s total number of neutrons and protons.
• Elements can be classified as being either metals, non-metals, or metalloids.
• Metals are elements that usually conduct heat and electricity and are shiny.

• Non-metals do not conduct electricity and are normally not shiny.
• Metalloids have characteristics that are in between metals and nonmetals.
• Elements with a net positive or negative charge are called ions.
• Compounds and molecules constructed in living tissues are commonly called organic.
• Forms of matter not formed by living things are termed inorganic.

• There are four general categories of organic compounds: Lipids, Carbohydrates, Proteins and Nucleic acids.

Atmosphere

• The atmosphere is the body of air which surrounds our planet.

• Most of our atmosphere is located close to the earth’s surface where it is most dense.

• The air of our planet is 79 % nitrogen and just under 21% oxygen; the small amount remaining is composed of carbon dioxide and other gases.

• The greenhouse effect is a naturally occurring process that aids in heating the Earth’s surface and atmosphere.

• It results from the fact that certain atmospheric gases, such as carbon dioxide, water vapor and methane, can change the energy balance of the planet by absorbing long wave radiation emitted from the Earth’s surface.

Structure of the Atmosphere

• The atmosphere has a layered structure, because of density stratification as a result of which lighter gases move up and denser ones settle down

• The lowermost part of the atmosphere in which we live, and which is the theatre for almost all the weather phenomena is known as the troposphere.

• Troposphere literally means the region of mixing and has been derived from the Greek word ‘Tropos’, meaning mixing or turbulence.

• The height of the troposphere at the poles is about 8 km, while at the equator it is about 16 km.

• This is because there is greater heating at the equator.

• Above troposphere is the stratosphere, which is important primarily because of the presence of ozone.

• This layer of calm and clear air is preferred for high-speed jet flights because of the absence of air pockets.

• Above stratosphere is the mesosphere, which more of a transitional layer.

• Above mesosphere lies the ionosphere, which has electrically conducting layers that help in radio communication.

• There are two important layers in the ionosphere viz. E layer or Kennelly Heavy side layer that reflects the medium radio waves, thus helping in short distance radio communication and F layer or Appleton layer that reflects the short radio waves and helps in long distance radio communication.

• The outermost layer of the Earth’s atmosphere is known as the Exosphere. It is so highly rarefied a region that its boundary is not clear.

Lithosphere

• The lithosphere is an Earth’s outermost layer, composed of rocks in the crust and upper mantle that behave as brittle solids.

• The rigid lithosphere sits on the top of the asthenosphere, a layer of the mantle in which rocks are hot and deformable.

• The lithosphere is the solid, rocky crust covering the entire planet. This crust is inorganic and is composed of minerals.

• It covers the entire surface of the earth from the top of Mount Everest to the bottom of the Mariana Trench.

• The actual thickness of the lithosphere varies considerably, and can range from roughly 40 km to 280 km.

• Earth’s lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth.

• The lithosphere is subdivided into tectonic plates.

• The lithosphere ends at the point when the minerals in the earth’s crust begin to demonstrate viscosity and fluid behaviours.

Rocks

• The earth’s crust is formed of mineral materials called rocks.

• The rocks which form the substructure of our lithosphere are grouped into three broad categories:

Igneous Rocks

• Igneous rocks are formed by the solidification of molten magma from the interior of the earth.

• About 95% of the earth’s crust is made of this type of rock. In fact, all other types of rocks originate from these rocks, and therefore, they are also called primary rocks.

• Igneous rocks are of three types.

Characteristics of Igneous Rocks

• The igneous rock does not contain layers.

• They are without fossils and the upper part of the rock contains joints.

• They are formed by volcanic lava.

• They are crystalline rocks and impervious rocks.

• They are massive and the weathering effect is difficult over them.

• They are primary rocks of the crust, hence are also called the primary rocks.

Sedimentary Rocks

• These rocks are formed from the sediment deposits on the ocean beds.

• They comprise only about 5% of the earth’s crust but cover about 75% of the total land surface.

• These rocks are made up of the weathered remains of igneous rocks, but also contain organic matter from the remains of marine organisms.

• Sedimentary rocks are formed in horizontal layers, called strata and take millions of years to harden into rocks.

• These rocks are also known as stratified rocks because of these layers.

• Although three-fourths of the earth’s surface is covered with sedimentary rocks, they make up for only 5 per cent and get broken into fragments, further reduced into small particles called sediments.

• These are derived from igneous, metamorphic or older sedimentary rocks.

• For this reason, these are known as sedimentary or fragmental rocks.

Characteristics of Sedimentary Rocks

• These rocks are porous, and they are stratified and without pores.

• They are affected by erosive forces easily.

• These rocks are formed by the rock sediments, fossils and vegetative material, so they contain more calcareous and carbonaceous contents.

• They possess joints and stratification.

• Most of the rocks of this type are formed by sedimentation on the floors of water bodies.

• These rocks are easily breakable due to softness.

Metamorphic Rocks

• Change is the rule of nature.

• This change is also seen in rocks.

• Pressure and heat bring a partial or whole change in rocks.

• Sometimes the physical properties of the original rock are entirely different from that of newly formed rock.

• This type of change is known as the Metamorphism and the rocks formed by this process are known as Metamorphic Rocks.

• The word Metamorphic is derived from the Greek word Metamorphosis, which means change.

• This change is found in texture, colour, hardness, and mineral composition of rocks.

• This metamorphosis is brought about by the pressure and heat of the layer mass over each other in Sedimentary and Igneous rocks.

Characteristics of Metamorphic Rocks

• These rocks are formed by intense pressure, heat and the chemical action over the rocks.

• They are formed by the metamorphosis in sedimentary and igneous rocks.

• They are formed in the solid state.

• They are formed at the depth of thousands of kilometres and there are no fossils in them.

Hydrosphere

• A hydrosphere is the total amount of water on a planet.

• The hydrosphere includes oceans, rivers and lakes. It also exists below ground as groundwater, in wells and aquifers.

• Water vapor is most visible as clouds and fog.

• The frozen part of Earth’s hydrosphere is made of ice: glaciers, ice caps and icebergs.

• The frozen part of the hydrosphere has its own name, the Cryosphere.

• The hydrologic cycle is a conceptual model that describes the storage and movement of water between the biosphere, atmosphere, lithosphere, and the hydrosphere.

• Water on this planet can be stored in any one of the following reservoirs: Atmosphere, Oceans, Lakes, Rivers, Soils, Glaciers, Snow fields, and Groundwater.

• Water moves from one reservoir to another by way of processes like evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration and melting and groundwater flow.

Biosphere

• The biosphere is the layer of the planet Earth where life exists.

• The term ‘biosphere’ is also used to describe a self-contained ecosystem such as the biospheres that are being tested for the future colonization of Mars.

• It is composed of all living organisms.

• Plants, animals, and one-celled organisms are all part of the biosphere.

• Most of the planet’s life is found from three meters below the ground.

• The biosphere is made up of biomes.