exam cram Flashcards
what is a grid
a grid is a network of vertical and horizontal lines on a map or a glob used for locating places
what a geographic grid
a geographic grid is the internationally recognized system of latitude and longitude used to locate positions on the earths surface
define equator
the equator is an imaginary line that runs horizontally through the centre of the earth dividing it into the northern and souther hemisphere
what is the 0 degree latitude and is equidistant from the north pole and south pole and used as a reference point for latitudes
equator
describe heat zones briefly
heat zones have developed on earth due to difference in insolation at different latitudes
describe the three heat zones
torrid zone: recieves direct rays of the sun and is the hottest zones, extends from tropic of cancer to the tropic of capricorn
temperate zone: sun is never directly overhead and rays are inclines, has a mild climate ranging from warm to cool, found between tropic of cancer and arctic circle in the northern hemisphere, found between tropic of capricorn and antarctic circle in southern hemisphere
frigid zone: remains frozen and is the coldest part of earth. in northern hemisphere, it lies between arctic circle and north pole, in southern hemisphere it lies between antarctic circle and south pole
define longitudes
Longitudes represent the east-west location of a place on the surface of the earth
why is standard time more scientific than local time
local time varies from meridian to meridian, creating confusion of time when one travels, covering multiple longitudes
to avoid confusion countries follow a uniform time based on central longitude of the country
the local time of that longitude is accepted as the countries standard time thus is it more scientific
why are time zones necessity for some countries
some countries have large east-west longitudinal extent leading to a larger time difference between parts of the country.
One standard time zone is impractical therefore multiple are needed
why is equator the only great circle among latitudes
a great circle is any circle whose centre meets with the center of the earth dividing into 2 halves. The equator is the only latitude which does so.
which longitude is considered as the idl.
the idl coincides with 180 degree longitude but deviates at places to avoid confusion
where does the idl pass thru?
it passes from one pole to the other through the pacific ocean
give 3 points of difference between latitude and longitude
latitudes represents north-south location of a place while longitudes represent east-west location of a place
latitudes are measured 0 to 90 degrees while longitudes are measured 0 to 180 degrees
latitudes represent heat zones and longitudes represent time zones
give 3 points of difference between equator and prime meridien
equator is the longest latitude, prime meridien is used as a reference for other meridians
equator is at 0 degree latitude while the prime meridian is a meridian at 0 degrees
equator divides the world into northern and southern hemisphere while prime meridian divides world into eastern and western hemisphere
give 3 points of difference between local time and standard time
local time is based on natural phenomena like the movement of the sun while standard time is based on central longitude of country
local time does not change if one stays in the same place while standard time is the official time of the whole country.
local time varies by 4 minutes for every degree of longitude while places on the same longitude have different standard times
give 3 points of difference between IST and GMT
indian standard time is the standard time in india while gmt is the reference through which other zones are measured
ist is 5 and half hours in front of gmt, gmt is accepted by all countries
ist passes through mirzapur, near allahabad in up, gmt passes through greenwich, england
define the prime meridian
a line of longitude which is 0 degrees, used as a reference for other meridians of longitude which is east or west of it, divides the world into east and west hemispheres.
define the idl
an imaginary line running north to south through the pacific ocean and coincides with the 180 degree longitude
define longitudes
angular distance of a location that it makes with the centre of the earth.
why are latitudes known as parallels of latitude
this is because they run horizontally to each other
why are latitudes and longitudes expressed in angles
if we draw a line from the centre of the earth to a spot it will give an angle
why is the distance of 1 degree difference in latitude 111 km
the circumference of the earth is 40000 km, the equator is a great circle and the circumference of the great circle equals to 360 degrees,hence the distance is 40000/360 = 111km
why is the torrid zone hotest
because it receives direct rays of the sun
why is the region beyond arctic cold
this is because it lies in a region which receives extremely slanted rays of sunlight
why are longitudes called meridians
because meridian is midday and when the sun is overhead at a longitude it is midday for that longitude.
why is the difference in time between gmt and ist 5 hrs 30 mins
this is because ist is 82.5 e based on this meridian it is calculated that the IST is 5 hrs 30 mins ahead
why does the usa have 5 timezones
this is due to the vast east-west longitudinal extent so one time timezone would be impractical due to the large time difference
why is the IDL not a straight line
it zigzags in order to avoid splitting countries into 2 days.
what are the different layers of the earth
outer silicate solid crust, viscous mantle, liquid outer core, solid inner core
how do the layers of the earth differ from each other
differ by size, chemical composition and density
what is the cause of increase of temperature in the interior of the earth
the temp. within the earth increases by 1 degree for every 32 m of descent
what is the composition of the earth
crust of earth is composed of rocks rich in silicates, aluminium and magnesium
distinguish between SIAL and SIMA
the upper layer of the crust (sial) called continental crust is made up of rocks rich in silicates and aluminium. The lower layer of the crust (sima) called oceanic crust is made up of rocks rich in silicates and aluminium
what is mohorovicic discontinuity
the boundary the mantle from the crust
briefly describe upper mantle
low velocity zone made of molten ultrabasic rocks, comprised mainly of silica and iron. called the asthenosphere which is 100km beneath the earths surface
briefly describe lower mantle
made up of solid ultrabasic rock, is dense and highly rigid, mainly contains iron and silica
mention 3 characteristics of the earths core
outer core has properties of liquid while inner core has properties of solid
has average temperature of 5500 degrees
mainly contains iron and nickel and is dense
why are rocks found in a molten state in the interior
due to extreme temperature
why is the lithosphere a solid layer of the earth
because it is the topmost layer made up of solid rocks
why is sial less dense than other layer
it forms the continental land that floats on a sea of dense sima
why is inner core solid
due to immense pressure
why do plates move on the crust of the earth
because they are placed above a semi molten layer of rocks
define an earthquake
sudden tremors felt on the surface of the earth
what is seismicity
type and size of earthquakes and their frequency over a period of time
define seismology
the scientific study of earthquakes and the propagation of elastic waves through the earth
define seismologists
geophysicists who study earthquakes and the mechanical characteristics of the earth
define seismologist epicenter
the point on the earth directly above the focus is the earthquakes epicentre
what is the difference between a seismometer and a seismograph
an instrument which measures the intensity of seismic activities, when seismic activities are recorded on a graph paper, it is called a seismograph