What is filtering? give an example of how this might take place in a city.

Opposite of gentrification. for example, a residential housing older than the new ones will become affordable for families with lower income

Filtering is opposite of the gentrification

Explanation:

As the higher income family households tend to move on, they now leave there older homes or the apartments that were earlier occupied and now are sold or rented to other families with more modest incomes. As the homes become old they are sold out. And the resident abandoned them for somewhere else. As the trends of the gentrification are out and the filtering is growing.

Answer volcanic outgassing;