Land

Physical science

The study of land and its history is called geography, while mineralogy examines minerals and petrology studies rocks. Soil science includes pedology, which focuses on soil formation, and edaphology, which examines the relationship between soil and life. In the nebular hypothesis, a solar nebula collapsed gravitationally, spinning into a circumstellar disc from which planets grew as planetesimals accumulated by clumping and gravity. Volcanic activity and outgassing produced Earth's atmosphere and oceans, with water vapour condensing and being augmented by water from asteroids, protoplanets, and comets.

Greenhouse gases kept oceans from freezing despite the young Sun's lower luminosity. By about 4.2 billion years ago, Earth's magnetic field was established, shielding the atmosphere from solar wind. The crust formed when the molten outer layer cooled, and once land could support life, biodiversity expanded over hundreds of millions of years, interrupted only by mass extinctions.

Features

A landform is a natural or manmade feature of the land, and together landforms create terrain whose arrangement is called topography. Landforms include hills, mountains, canyons, valleys, and shoreline features such as bays, capes, and peninsulas. The shoreline, where land meets the ocean, migrates daily with tides and over long periods as sea levels change.

The shore extends from the low tide line to the highest reach of storm waves, while the coast stretches inland until ocean-related features disappear. When land contacts water, erosion can occur, influenced by tides caused by gravitational forces. Coasts are important ecosystems, often hosting freshwater or estuarine wetlands that support birds and other terrestrial animals.

Wave-protected areas may contain saltmarshes, mangroves, or seagrasses that serve as nursery habitats for fish and shellfish. Rocky shores on exposed coasts provide habitat for sessile animals like mussels, starfish, and barnacles, as well as seaweeds. In tropical, clear, nutrient-poor waters, coral reefs are often found between depths of 1 and 50 meters.

Humans and land

Land is deeply intertwined with human development, serving as a crucial resource for survival and a source of subsistence. Access to land can determine survival and wealth, especially in developing countries, creating complex power relationships in production and consumption. Most world philosophies and religions recognize a human duty of stewardship toward land and nature.

Many people see land as a source of spirituality, inspiration, and beauty, and derive a sense of belonging from it, particularly if it belonged to their ancestors. Various religions teach about a connection between humans and land, such as the veneration of Bhumi in Hinduism and the obligation to protect land as hima in Islam. Almost every Indigenous group has etiological stories about the land they inhabit, and for Indigenous peoples, connection to land is an important part of identity and culture. Some religious groups consider particular areas sacred, like the Holy Land in Abrahamic religions.

Creation myths in many religions involve a supernatural deity separating land from oceans and air. Ancient Egyptian mythology differs in that Earth (Geb) is male and the sky (Nut) is female. Ancient Near Eastern cultures viewed the world as a flat disk of land surrounded by ocean, a concept echoed in the Hebrew Bible and Homeric accounts.

Environmental issues

Land degradation is the reduction or loss of biological or economic productivity and complexity of land due to human activity, driven by agriculture, urbanization, energy production, and mining. Humans have altered more than three-quarters of ice-free land through habitation and other use, fundamentally changing ecosystems. Human activity is a major factor in the Holocene extinction, and human-caused climate change is causing rising sea levels and ecosystem loss.

Environmental scientists study land's ecosystems, natural resources, biosphere, troposphere, and the impact of human activity, leading to international action to prevent biodiversity loss and desertification and to encourage sustainable forest and waste management. The conservation movement lobbies for protecting endangered species and natural areas such as parks. International frameworks, notably the United Nations' Sustainable Development Goals, focus on how humans can meet needs while using land more efficiently and preserving natural resources. Human land use can degrade soil quality and quantity through agrochemicals, infrastructure development, and mining.

Physical processes like erosion, sealing, and crusting cause structural breakdown, preventing water penetration and causing runoff. Chemical processes such as salinization, acidification, and toxication create imbalances; salinization affects at least 20% of all irrigated lands, reducing agricultural productivity. Tillage can alter biological processes, leading to excessive mineralization and nutrient loss.

Did You Know?

• The word land derives from Proto-Germanic landą, meaning 'untilled land', and ultimately from Proto-Indo-European lendʰ-.
• Many country names incorporate the suffix -land (e.g., England, Greenland) or the equivalent -stan from Indo-Iranian (e.g., Pakistan, Afghanistan).
• The pedosphere is the outermost layer of Earth's continental surface, composed of soil and subject to soil formation processes.