Diffusion

Mobility and Diffusion

Definition of Diffusion

• Diffusion: A specific type of mobility that refers to movement from an origin point outward to other locations.

Types of Diffusion

• Geographers categorize diffusion into two primary types: Relocation Diffusion and Expansion Diffusion.

Relocation Diffusion

• Definition: Occurs when a trait stops in one location and picks up again in another location without an increase in the number of adopters.

• Characteristics:

  • The total number of adopters remains the same.

  • Locations of adopters change.

• Example:

  • Pizza Restaurants: The closure of a pizza restaurant in one city and its reopening in another city illustrates relocation diffusion. The total number of restaurants remains the same, but their locations are different.

Expansion Diffusion

• Definition: Occurs when the number of trait adopters increases as a trait spreads outward.

• Characteristics:

  • The total number of adopters grows.

  • Both the spread of the trait and the prevalence of that trait among adopters increase.

• Example:

  • Pizza Restaurants: New pizza restaurants opening in various locations demonstrates expansion diffusion, where the total number of restaurants increases.

Types of Expansion Diffusion

• Expansion diffusion can occur in two distinct ways:

  1. Hierarchical Diffusion

  2. Contagious Diffusion

Hierarchical Diffusion

• Definition: A diffusion process characterized by a leapfrog effect where a trait skips areas and first appears in larger, distant cities.

• Mechanism:

  • Large cities tend to have stronger interaction networks, allowing traits to spread first to them before extending to medium and smaller cities.

• Example: Initial diffusion of a trait in major cities, followed by gradual spread to smaller towns.

Contagious Diffusion

• Definition: A process where a trait spreads outward like a wave, primarily based on proximity to adopters.

• Mechanism: The trait spreads quickly to nearby places before eventually reaching more distant locations.

• Example:

  • Islam Diffusion: The spread of Islam from the Arabian Peninsula based on proximity, showing contagious diffusion characteristics.

Historical Examples of Expansion Diffusion

• Islam's Expansion: From the seventh century AD to the seventeenth century, with a clear demonstration of contagious diffusion.

• Christianity's Early Spread: 300 to 1100 AD, with varying spread patterns:

  • Scattered early adopters concentrated in urban settings, displaying hierarchical diffusion characteristics.

Case Study: Solar Panels in Connecticut

• Study Overview:

  • Maps from 2005, 2008, and 2013 illustrate solar panel installations.

  • Green areas represent population density, while yellow dots indicate solar panel installations.

• Findings:

  • Yellow dots do not align with areas of highest population; installations occurred in both rural and urban areas.

  • Neighbor effects observed: Adding a solar system in a neighborhood increased installations within a half-mile radius.

  • Conclusion: This example clearly exhibits contagious diffusion, not hierarchical diffusion.

Stimulus Diffusion

• Definition: A type of diffusion where a specific trait fails to spread, but the underlying idea is adapted and changed to meet local circumstances.

• Researcher: Cultural anthropologist Alfred Kroeber.

• Example:

  • Egyptian Hieroglyphics: Some scholars suggest hieroglyphics may be based on Sumerian cuneiform:

  • Cuneiform: The oldest known form of writing, dating from around 3,500 to 3,000 BC, showing an evolutionary development.

  • Hieroglyphics, which used the principle of written communication from cuneiform, emerged uniquely in Egypt around 3200 BC suggesting a rapid development influenced by contact with Sumerian technologies.