What are the lines that run east-west on the Earth known as?

The lines that run east-west on Earth are known as parallels of latitude. These lines are used in geographical coordinate systems to indicate the location of different points on the Earth's surface. Each parallel is a line of constant latitude, meaning that they are all horizontal lines relative to the Earth’s axis.

Parallels of latitude are significant because they help define the climate zones of the Earth, as they correspond to different distances from the equator. For example, the equator is at 0 degrees latitude, and as one moves towards the poles, the latitude increases.

These parallels are crucial for navigation and mapping, as they provide a consistent framework for understanding the geographic layout of the planet. It's important to note that while meridians of longitude run north-south and intersect at the poles, the parallels of latitude provide a grid system that allows for the easy identification and referencing of locations around the globe.