Answer:
The spatial distribution of populations and settlements across a country and their interconnectivity and accessibility from urban areas are important for delivering healthcare, distributing resources and economic development. However, existing spatially explicit population data across Africa are generally based on outdated, low resolution input demographic data, and provide insufficient detail to quantify rural settlement patterns and, thus, accurately measure population concentration and accessibility. Here we outline approaches to developing a new high resolution population distribution dataset for Africa and analyse rural accessibility to population centers. Contemporary population count data were combined with detailed satellite-derived settlement extents to map population distributions across Africa at a finer spatial resolution than ever before. Substantial heterogeneity in settlement patterns, population concentration and spatial accessibility to major population centres is exhibited across the continent. In Africa, 90% of the population is concentrated in less than 21% of the land surface and the average per-person travel time to settlements of more than 50,000 inhabitants is around 3.5 hours, with Central and East Africa displaying the longest average travel times. The analyses highlight large inequities in access, the isolation of many rural populations and the challenges that exist between countries and regions in providing access to services. The datasets presented are freely available as part of the AfriPop project, providing an evidence base for guiding strategic decisions.
Explanation:
Earthquakes produce P and S waves. The P waves are fast and of a higher frequency than S waves. P waves reach a point first and can pass through liquid media while S waves reach after and the lose much of their energy while passing liquid media. This is because S-waves are shear waves and require rigid/inelastic media for transmission.
During an earthquake, there is usually a shadow zone (where there is no destruction because S-waves did not reach) formed right above the epicenter of the earthquake. This is due to the fact that the S-waves were unable to transit through the liquid inner core of the earth before reaching the earth's surface. Only P-waves are registered in this shadow zone.
The Arctic Ocean is the shallowest ocean in the world.
Deserts, grasslands, mountains, and tropical coastlines are what make up China’s landscape! It harbors some of the most extreme climates in the world because it is so large.
