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Matter

Matter is any substance that has mass and takes up space. Earth, and everything on it, is made of matter, and so are all the stars and planets in the ...

Population Density

Population density is the concentration of individuals within a species in a specific geographic locale. Population density data can be used to quanti...


The Great Wall of China

The Great Wall of China was built over centuries by China’s emperors to protect their territory. Today, it stretches for thousands of miles alon...


Linguistics

Linguistics, the study of language, gives us a window into the way we communicate.


Sustainable Development Goal 11: Sustainable Cities and Communities

Sustainable Development Goal 11, one of 17 goals that make up the United Nation’s 2030 Agenda for Sustainable Development, provides targets and ...

Feng Shui

Feng Shui is an ancient Chinese art of arranging buildings, objects, and space in an environment to achieve harmony and balance in a way that will bri...



Plate Boundaries

Earth’s tectonic plates fit together in a jigsaw puzzle of plate boundaries.

Demography

Demography is the statistical study of human populations. Demographers use census data, surveys, and statistical models to analyze the size, movement,...


Cloud Cover

Cloud cover is an important component of understanding and predicting the weather. Not only does cloud cover impact sky conditions and inform precipit...


Water-Worlds

The collection of water on our planet—in the ocean, the ground, and the atmosphere—collectively forms the hydrosphere, making it a water-w...


Photosynthesis

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Atmosphere

Earth’s atmosphere is so much more than the air we breathe. A trip from the surface of Earth to outer space would result in passing through five...



Intertidal Zone

The intertidal zone is an ecosystem found on marine shorelines, where a multitude of organisms living on the shore survive changes between high and lo...

Role of Keystone Species in an Ecosystem

A keystone species helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist alt...


Evaporation

Evaporation is the process by which a liquid turns into a gas. It is also one of the three main steps in the global water cycle.


Groundwater

Groundwater is water that has infiltrated the ground to fill the spaces between sediments and cracks in rock. Groundwater is fed by precipitation and ...


Aquifers

An aquifer is a body of porous rock or sediment saturated with groundwater. Groundwater enters an aquifer as precipitation seeps through the soil. It ...

Water Table

The water table is the boundary between the unsaturated zone and the saturated zone underground. Below the water table, groundwater fills any spaces b...



Wildfires

A wildfire is an uncontrolled fire that burns in wildland vegetation, often in rural areas.

Deforestation

Deforestation is the intentional clearing of forested land.


Controlled Burning

Controlled burns are an important tool for maintaining the health and safety of a forest.


Ocean Currents

Ocean currents are like vast rivers, flowing along predictable paths.


Distribution of Forests

Forests are important environments for biodiversity and storing carbon. How much of the planet is covered by trees and how has that percentage changed...

Global Warming

The Earth is warming up, and humans are at least partially to blame. The causes, effects, and complexities of global warming are important to understa...



Greek City-States

The Greek city-states were the dominant settlement structure of the ancient Greek world and helped define how different regions interacted with each o...