Physical Geography Flashcards
Inaugurator of geography/coining of term
Eratosthenes
Shape of earth
Geoid- spherical but flattened at poles
Geographical Information system (GIS)
Collects and manipulates data to create maps
Global Navigation Satellite System (GNSS)
To find out the exact location of something on the earth. Also called GPS (USA), GLONASS (Russia), IRNSS (India) etc.
Theories of the origin of planets/ earth
Nebular hypothesis by Laplace and Immanuel Kant- from cloud of rotating material
Chamberlain and Moulton considered that a wandering star approached the sun. As a result, a cigar-shaped extension of material was separated from the solar surface. As the passing star moved away, the material separated from the solar surface continued to revolve around the sun and it slowly condensed into planets
Accretion theory- Schmidt and Weizascar- nebula of hydrogen helium spun and collapsed on itself due to gravity, forming disc shaped cloud and clumps and bunching- heavier stuff stuck together (rocky planets), lighter flew away (gas giants).
Origin of the universe theory
Big Bang theory/expanding universe hypothesis by Lemaitre and Hubble- 13.75 billion years ago rapid expansion in a millisecond from a single atom of small volume, infinite temperature and infinite density, it exploded, some energy converted to matter, Within 300,000 years from the Big Bang, temperature dropped to 4,500 K (Kelvin) and gave rise to atomic matter. The universe became transparent.
Hoyle’s concept of steady state. It considered the universe to be roughly always the same.
Formation of stars
Nebula (cloud of matter) develops localised clumps of gas. These clumps continue to grow into even denser gaseous bodies, giving rise to formation of stars.
Earth age
4.6 billion years
Evolution of lithosphere of the earth
Separation of material into different layers depending upon density. Heavy sank to centre, lighter floated upwards. With time, cooling, solidification and condensation into crust. Moon collision further shook things up before settling again. Differentiation.
Evolution of Atmosphere of the earth
The first stage is marked by the loss of the primordial atmosphere of hydrogen and helium due to solar winds. In the second stage, the interior of the earth released gases (nitrogen, carbon dioxide, methane, ammonia and very little free oxygen) The process through which the gases were outpoured from the interior is called degassing and water vapour condensed contributed to the evolution of the atmosphere. Finally, the composition of the atmosphere was modified by the living world through the process of photosynthesis.
Evolution of Hydrosphere of the earth
Degassing (through volcanic eruptions) contributed water vapour and gases to the atmosphere. As the earth cooled, the water vapour released started getting condensed. The carbon dioxide in the atmosphere got dissolved in rainwater and the temperature further decreased causing more condensation and more rains. The rainwater falling onto the surface got collected in the depressions to give rise to oceans. The earth’s oceans were formed within 500 million years from the formation of the earth. Sometime around 3.8 billion years ago, life began to evolve. However, around 2.5 billion years before the present, the process of photosynthesis evolved. Oceans began to have the contribution of oxygen through the process of photosynthesis. Eventually, oceans were saturated with oxygen, and 2 billion years ago, oxygen began to flood the atmosphere.
Inner and outer planets
mercury, venus, earth and mars are called as the inner planets as they lie between the sun and the belt of asteroids the other four planets are called the outer planets.
Jovian planets
The outer four are called Jovian or Gas Giant planets. Jovian means jupiter -like.
Difference between terrestrial and jovian planets
(i) The terrestrial planets were formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles. Jovian planets were formed at quite a distant location.
(ii) The solar wind was most intense nearer the sun; so, it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.
(iii) The terrestrial planets are smaller and their lower gravity could not hold the escaping gases.
Moon formation
Sir George Darwin suggested that initially, the earth and the moon formed a single rapidly rotating dumbbell shaped body, and it broke off. Now believed that outcome of ‘giant impact’ or “the big splat”. A body of the size of one to three times that of mars collided into the earth, blasted a large part into space which eventually formed into the present moon about 4.44 billion years ago.
Evolution of life on earth
Modern scientists refer to the origin of life as a kind of chemical reaction, which first generated complex organic molecules and assembled them. This assemblage was such that they could duplicate themselves converting inanimate matter into living substance sometime 3,800 million years ago.
Formation of planets
Nebula becomes star by bunching and clumping. The gas cloud starts getting condensed and the matter around the core develops into small- rounded objects by the process of cohesion and collision develop into planetesimals. Large number of small planetesimals accrete to form a fewer large bodies in the form of planets.
Phases of the moon
Full Moon- Poornima- once a month, entire visible
New Moon- Amavasya- completely disappeared
Each occur a fortnight apart
Celestial bodies
Objects shining in the night sky
Stars
Made up of gasses, emit their own heat and light. Sun, and nearest to it is Proxima Centauri
Constellations
Patterns formed by stars
Pole Star
Aka north star, fixed position and indicates north
Planets
Celestial bodies that do not emit own heat and light
Planets in solar system number and name
8- Mercury venus earth mars jupiter saturn uranus neptune
Which planets have debris/ rings
jupiter saturn uranus
Light travel speed
300,000 km per second
Composition of solar system
Sun, 8 planets, asteroids and meteoroids
Discuss the sun
Hydrogen (70%), Helium (27%), remaining gasses (3%). Provides gravity that keeps solar system together.
Six main regions- Interior- 1.core where nuclear fusion (combo) occurs 2.radiative zone energy transported by photons i.e electromagnetic waves 3.convective zone- energy movement via fluids like gasses. Exterior- 4.photosphere- visible surface 5.chromosphere- giving reddish hue 6.corona-hotter than sun surface, transitions into solar wind
Discuss Mercury
Smallest, no satellite, second hottest
Discuss Venus
Earth’s twin, hottest planet, aka morning/evening star
Discuss Earth
1 orbit- 365 days, 1 rotation on axis- 1 day. Sunlight takes 8.2 minutes to reach
Discuss Mars
Similar landmass, reddish due to iron oxide, 2 moons
Discuss Jupiter
Largest gas giant, ring system, 79 moons
Discuss Saturn
Avg density less than water, rings, 82 moons
Discuss Uranus
Frigid, rings, 27 moons
Discuss Neptune
Coldest and windiest, 13 moons
Dwarf planets
Small celestial bodies that revolve around the sun. Pluto was demoted because it could not clear orbit of other debris. Other eg- Ceres
Satellite
Celestial bodies that revolve around planets, can be artificial also
Discuss Our Moon
27 days to rotate and revolve, thus only one face shows
Asteroids
Bodies that move around the sun, are found in the belt between mars and jupiter, aka minor planets.
Comets
Objects made of ice particles and gasses that move around the sun, have a distinctive tail. Found in Kuiper Belt- between Neptune to 50 AU from sun.
Meteoroids
Asteroids that have been removed from the belt, which sometimes enter earth atmosphere and burn
Axis
Imaginary line passing through the poles on which the earth spins
Equator
Imaginary line divind the earth into two parts- northern and southern hemisphere
Parallels of latitudes
All circles parallel to the equator upto the poles, measured in degrees
Important Parallels of latitudes
0 degree equator
North pole 90 degree N
South pole 90 degree S
Tropic of cancer 23 ½ degree N
Tropic of capricorn 23 ½ degree S
Arctic circle 66 ½ degree N
Antarctic circle 66 ½ degree S
Heat zones of the earth
Torrid- between Tropic of cancer 23 ½ degree N and Tropic of capricorn 23 ½ degree S
Temperate between-Tropic of cancer 23 ½ degree N-Arctic circle 66 ½ degree N and Tropic of capricorn 23 ½ degree S and Antarctic circle 66 ½ degree S
Frigid- North pole 90 degree N- Arctic circle 66 ½ degree N and South pole 90 degree S- Antarctic circle 66 ½ degree S
Longitudes
Imaginary perpendicular lines, measured in degrees minutes seconds-1 degree= 6 minutes. Prime meridian that divides earth into eastern and western hemispheres is at Greenwich observatory i.e. 0 degrees and the 180 degree longitudes E and W overlap and is the International date line.
IST
5:30 more than greenwich, longitude of 82 ½ degree N
Rotation
Spinning of earth on axis, determine day-night, tides, coriolis force, geoid bulge. Axis is tilted 66 ½ degrees from orbital plane and 23 ½ degrees perpendicular plane. 23 hours 56 minutes (earth day)
Revolution and orbit distances from sun
Movement of earth around sun in elliptical path- causes seasons, variations in day-night lengths, and variations in solar energy distribution. Avg 150 million km from sun which becomes Aphelion 152 mkm and Perihelion 147 mkm. 365 days 6 hours.
Summer solstice
21st June Sun directly overhead the tropic of cancer, max heat, and N pole 6 months of continuous daylight. Longest day and shortest night for N. Opposite in S hemisphere.
Winter Solstice
22nd December- Sun directly overhead the tropic of capricorn, max heat, and S pole 6 months of continuous daylight. Longest day and shortest night for S. Opposite in N hemisphere.
Equinox
Neither poles tilted towards sun, so whole earth experiences equal days and nights. 21st March Vernal, 23rd September Autumnal- rays of sun fall directly on equator.
What influences landscape development?
Endogenic processes happening inside the earth as well as exogenic processes happening outside.
Sources for the interior of the earth
Direct sources- mining, volcanic eruptions. Indirect sources- studying properties of matter, meteors, gravity, magnetic fields, seismic activity.
Discuss the gravitational force on earth
The gravitation force (g) is not the same at different latitudes on the surface. It is greater near the poles and less at the equator. This is because of the distance from the centre at the equator being greater than that at the poles. The gravity values also differ according to the mass of material. These readings differ from the expected values. Such a difference is called gravity anomaly. Gravity anomalies give us information about the distribution of mass of the material in the crust of the earth.
Earthquake
An earthquake is the shaking of the earth due to release of energy, which generates waves that travel in all directions.
Cause of earthquake
The release of energy occurs along a fault. A fault is a sharp break in the crustal rocks. Rocks along a fault tend to move in opposite directions. As the overlying rock strata press them, the friction locks them together. However, their tendency to move apart at some point of time overcomes the friction. As a result, the blocks get deformed and eventually, they slide past one another abruptly. This causes a release of energy, and the energy waves travel in all directions.
what is a fault?
sharp break in crustal rocks
Hypocentre/focus and epicentre of an earthquake
The point where the energy is released is called the focus of an earthquake, alternatively, it is called the hypocentre. The energy waves travelling in different directions reach the surface. The point on the surface, nearest to the focus, is called epicentre. It is the first one to experience the waves. It is a point directly above the focus.
Where do earthquakes take place?
All natural earthquakes take place in the lithosphere, the portion of depth up to 200 km from the surface of the earth.
What device measures earthquakes and what exactly does it do?
An instrument called ‘seismograph’ records the waves reaching the surface.
Types of earthquake waves
body waves and surface waves. Body waves are generated due to the release of energy at the focus and move in all directions travelling through the body of the earth. They are called P and S-waves. P-waves move faster and are the first to arrive at the surface. These are also called ‘primary waves’. The P-waves are similar to sound waves. They travel through gaseous, liquid and solid materials. S-waves arrive at the surface with some time lag. These are called secondary waves and can travel only through solid materials.
The body waves interact with the surface rocks and generate new set of waves called surface waves. These waves move along the surface. The surface waves are the last to report on a seismograph. These waves are more destructive.
Different names for P S and L waves
P- longitudinal
S- transverse
L- surface waves
Propagation of Earthquake Waves
The velocity of waves changes as they travel through materials with different densities. The denser the material, the higher is the velocity. P-waves vibrate parallel to the direction of the wave. This exerts pressure on the material in the direction of the propagation. As a result, it creates density differences in the material leading to stretching and squeezing of the material. Other three waves vibrate perpendicular to the direction of propagation. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass.
Shadow Zone
Areas where earthquakes are not recorded on seismographs due to refraction and reflection as they pass through the Earth’s layers.. Such a zone is called the ‘shadow zone’. For S waves, anything beyond 105 degree from epicentre, while for P waves between 105 and 145 degrees from epicentre. Thus, S wave shadow zone larger (40% of earth’s surface)
Types of earthquakes
(i) tectonic earthquakes. These are generated due to sliding of rocks along a fault plane.
(ii) A special class of tectonic earthquake- volcanic earthquake. However, these are confined to areas of active volcanoes.
(iii) In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors. These are called collapse earthquakes.
(iv) Ground shaking may also occur due to the explosion of chemical or nuclear devices. Such tremors are called explosion earthquakes.
(v) The earthquakes that occur in the areas of large reservoirs are referred to as reservoir induced earthquakes.
Measuring earthquakes scales
The earthquake events are scaled either according to the magnitude or intensity of the shock. The magnitude scale is known as the Richter scale. The magnitude relates to the energy released during the quake. The magnitude is expressed in numbers, 0-10. The intensity scale is named after Mercalli, an Italian seismologist. The intensity scale takes into account the visible damage caused by the event. The range of intensity scale is from 1-12.
layers of the earth
Crust, mantle, core
Discuss the crust
It is the outermost solid part of the earth. It is brittle in nature. The thickness of the crust varies-oceanic crust is 5 km, continental 30 km, mountain systems 70 km.This type of rock found in the oceanic crust is basalt. The mean density of material in oceanic crust is 2.7 g/cm3. Continental made up of heavier rocks having density of 3 g/cm3.
What is the lithosphere?
The crust and the uppermost part of the mantle are called lithosphere. Its thickness ranges from 10-200 km.
Discuss the mantle
Between crust and core. The mantle extends from Moho’s discontinuity to a depth of 2,900 km. 1.The upper portion of the mantle is called asthenosphere. The word astheno means weak. It is considered to be extending upto 400 km. It is the main source of magma. Density- 3.4 g/cm3.
2.The lower mantle extends beyond the asthenosphere. It is in solid state.
Discuss the core
The outer core is in liquid state while the inner core is in solid state. The density of material at the mantle core boundary is around 5 g/cm3 and at the centre of the earth at 6,300 km, the density value is around 13g/cm3. The core is made up of very heavy material mostly composed of nickel and iron. It is sometimes referred to as the nife layer.
What is a volcano?
A volcano is a place where gases, ashes and/or molten rock material – lava – escape to the ground.
Magma lava difference and constituents
The material in the upper mantle portion is called magma. Once it starts moving towards the crust or it reaches the surface, it is referred to as lava. The material that reaches the ground includes lava flows, pyroclastic debris, volcanic bombs, ash and dust and gases such as nitrogen, sulphur compounds and minor amounts of chlorene, hydrogen and argon. N SHAC
Types of volcanoes
1.Shield Volcanoes- are the largest of all the volcanoes on the earth, are made up of basalt, a type of lava that is very fluid when erupted. For this reason, these volcanoes are not steep, but since comes out in a fountain fashion, formation of cinder cone. Usually low explosivity, but explosive when water gets into the vent. Eg. Hawaii
2.Composite Volcanoes- These volcanoes are characterised by eruptions of cooler and more viscous lavas than basalt. These volcanoes often result in explosive eruptions. Along with lava, large quantities of pyroclastic material and ashes find their way to the ground. This material accumulates in the vicinity of the vent openings leading to formation of layers, and this makes the mounts appear as composite volcanoes.
3.Caldera-most explosive of the earth’s volcanoes so much that when they erupt they tend to collapse on themselves rather than building any tall structure. The collapsed depressions are called calderas. Their explosiveness indicates that the magma chamber supplying the lava is not only huge but is also in close vicinity.
4.Flood Basalt Provinces- outpour highly fluid lava that flows for long distances. Eg The Deccan Traps from India, presently covering most of the Maharashtra plateau.
5.Mid-Ocean Ridge Volcanoes- These volcanoes occur in the oceanic areas, and experience frequent eruptions in the central region. There is a system of mid-ocean ridges more than 70,000 km long that stretches through all the ocean basins.
Volcanic landforms types
Lava cools into igneous rocks which are classified as volcanic rocks (cooling at the surface) and plutonic rocks (cooling in the crust, assumes intrusive forms).
