In this Geoshortqa we are going to know about types of Sand Dunes. Types of Sand Dunes, Geoshortqa Sand Dunes Sand dunes are heaps of sand found in deserts . Generally , their heights vary from a few metres to 20m , but in some cases dunes are several hundred metres high and 5 to 8 km long . The formation of sand dunes requires • Wind of high velocity • Abundant sand • Obstacles such as trees , bushes , forests , rock outcrops , walls against , which dunes may settle • Ideal places i.e. dune complex , dune colony or dune chain . Dunes formed due to obstacles like hushes , walls etc. are called nebkhas , where dune formed besides desert depressions are called lunettes. Dunes are classified on the basis of morphology , structure , orientation , location , internal structure , ground pattern and number of slip faces . These are the various types of sand dunes a) Transverse Dunes are dunes deposited transverse to the prevailing winds direct...
In this Geoshortqa we know about Urban System
Urban System
There are different urban systems that co-exist together in any urban region of the world. These systems are classified on th basis of size and spatial distribution as there is a certain degree of organisation in their size and spatial order.
These urban systems include small towns, medium sized towns and large cities. To study the order of size relationship and spatial distribution, relation between city rank and city size (in terms of population) is to be examined. The Law of Primate city and Rank size rule depict the relation between the size and spatial distribution of towns.
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| Urban System, Geoshortqa |
Primate City
The law of Primate city by Mark Jefferso in 1939
Main theme :
The Law of Primate City is premised on the observation that the country's leading city is usually disproportionately larger than others in the system. e.g. Copenhagen is nine times the size of Aarhus etc. According to Jefferson, "Primate city has pre-eminence in infrastructure, economic, social and political affairs".
Rank size rule
The rank size rule by George Kingsley Zipf in 1949
Main theme :
Principle Rank size rule expresses the relationship between towns in mathematical terms and advocates that 'if all the urban settlements in an area are ranked in descending order of population, the population of the nth town will be 1/nth that of the largest town.'
Pn=P1/n
Where,
Pn = Population of town of rank n in descending order
P1 = Population of largest city
n = Value of rank
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