¿Porqué existen grandes aglomeraciones y vacíos demográficos? De ejemplos

Name the river that forms a natural border between new york and new jersey and is the site where a passenger jet made a miraculous landing on january 15

Which of the following is evidence to the past existence of glaciers?

Read the article titled "trans-saharan migration routes to north africa and the eu: historical roots and current trends." why do tens of thousands of sub-saharan africans try to cross the mediterranean each year? how are these refugees commonly portrayed? (site 1)