# AP Human Geography GRAVITY MODEL.

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AP Human Geography GRAVITY MODEL

What is a model? a representation of some phenomenon of the real-world made to facilitate an understanding of its workings a simplification and/or generalization of a complex reality from which the incidental detail has been removed an abstraction – not a reality

Types of geographic models
Mathematical Graphic Textual

What do you need to know about models?
The associated geographer The “parts” of the model The “assumptions” of the model Critiques of the model Applications of the model

Most Critical! A model IS NOT a “plan” to be followed in the future.
A model IS a “description” of what happened in the past. A model IS NOT a critique of the present. A model IS a pattern to which we can compare the present in order to see differences.

Tobler’s Law of Gravity
Waldo Tobler "Everything is related to everything else, but near thing s are more related than distant things.”

Gravity Model Uses size of location and distance as factors for travel
Size of location takes precedent over distance The gravity model can be used to estimate: Traffic Flows Migration between two areas The number of people likely to use one central place

The GRAVITY MODEL of MIGRATION is a model, derived from Newton's law of gravity.
Newton's law states that: "Any two bodies attract one another with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them."  The GRAVITY MODEL of MIGRATION is used to predict the degree of interaction between two places

When used geographically, the words 'bodies' and 'masses' are replaced by 'locations' and 'importance' respectively,. Importance can be measured in terms of population numbers, gross domestic product, or other appropriate variable.

The gravity model of migration is therefore based upon the idea that as the importance of one or both of the location increases, there will also be an increase in movement between them.

The farther apart the two locations are, however, the movement between them will be less.
This phenomenon is known as distance decay.

The simplistic version of the gravity model of migration is as follows:
Mij = gravity model prediction of migration between origin i and destination j Pi = population of origin State i Pj = population of destination State j dij = distance from origin i to destination j Mij= Pi*Pj dij2

CITY ATLANTA NEW YORK CITY KNOXVILLE AUSTIN LOS ANGELES CHICAGO TULSA
POPULATION (2012) ATLANTA 443,775 NEW YORK CITY 8,336,697 KNOXVILLE 182,200 AUSTIN 842,592 LOS ANGELES 3,857,799 CHICAGO 2,714,856 TULSA 393,987 COMPARE ATLANTA TO EACH OF THE CITIES LISTED

How might the calculations of distance you came up with differ from actual travel distances in real life? What other factors might influence people to travel to one city or another (other than distance decay)? How accurately do you believe the gravity model formula predicts actual migratory patterns between places? Explain.

Earnest Ravenstein (1885) 1) Most migrants only travel short distances to higher populated areas 2) Migrants created gaps through the flow towards the higher populated areas filling up space between origin and destination 3) Counter-current of migration at destination 4) Long distance migrants flock towards world cities or large industrial areas 5) The natives of towns are less migratory than those of the rural parts of the country 6) Females are more migratory than males Until recently Men, or couples w/o children, young adult or senior citizens, no dependents

Migration Issues Push factors Pull factors Forced Migration Refugees
Things that push people to move away from a location Pull factors Things that draw people to a location Forced Migration People forced to leave a given place permanently Usually based on ethnicity, religion, ideology, etc. Refugees People leaving a location for fear of persecution or death War-torn nations, religious persecution Cuban refugees Intervening obstacles Things that block migration streams Intervening opportunities Things that attract people while in the migration stream

Cultural Hearths The center or starting point of a cultural trait
Regions can be defined by hearths Examples? Vatican City Birth of Blues (Memphis, Tennessee)

Hierarchical diffusion Contagious diffusion Stimulus diffusion
Cultural Diffusion Relocation diffusion Hierarchical diffusion Contagious diffusion Stimulus diffusion Expansion diffusion

Assimilation Acculturation
The spread of a cultural complex or a cultural trait from one location to another The process of another culture embracing or adding that cultural trait to their cultural complex Assimilation A culture is completely dominated by another culture Forced migration Imperialization