Geomorphology

Geomorphology is the study of how the Earth's surface changes over time. It looks at features like mountains, valleys, and rivers to learn how they formed and how they might change in the future. This science uses ideas from physical geography, geology, and engineering geology.

Badlands incised into shale at the foot of the North Caineville Plateau, Utah, within the pass carved by the Fremont River and known as the Blue Gate. G. K. Gilbert studied the landscapes of this area in great detail, forming the observational foundation for many of his studies on geomorphology.

Geomorphologists try to explain why landscapes look the way they do. They study the history of landforms and how they might change. By watching, testing, and using computer models, they can predict future changes to the Earth's surface. This helps in many areas, like planning cities and understanding natural disasters.

Overview

Waves and water chemistry lead to structural failure in exposed rocks.

The Earth's surface changes because of natural forces. Water, wind, ice, plants, and even people shape the land. These forces work with the movement of the Earth's plates, which can lift up mountains or push land down. Climate also affects how landscapes change over time.

Geomorphologists study these changes to learn how landscapes form and evolve. They look at how rivers move sediment, how glaciers carve valleys, and how soil forms. They use tools like GPS and satellite images to measure and map the land. Their work helps predict natural hazards like landslides and guides efforts to protect rivers and coastlines. They also study similar processes on other planets, like Mars, to learn more about how planets change.

History

Geomorphology is a young science that started growing in the mid-19th century along with other earth sciences. This section looks at some important people and events in its history.

"Cono de Arita" at the dry lake Salar de Arizaro on the Atacama Plateau, in northwestern Argentina. The cone itself is a volcanic edifice, representing complex interaction of intrusive igneous rocks with the surrounding salt.

Ancient geomorphology

Studying landforms and how Earth's surface changes began with ancient scholars in Classical Greece. In the 5th century BC, Greek historian Herodotus observed soils and suggested the Nile delta was growing into the Mediterranean Sea. In the 4th century BC, Greek philosopher Aristotle thought seas would fill up and land would lower, swapping places in a cycle.

Other early ideas came from scholars in Arabic Basra and Persian scholar Abū Rayhān al-Bīrūnī in the 11th century. In 1546, German metallurgist and mineralogist Georgius Agricola wrote about erosion and natural weathering.

Early modern geomorphology

Lake "Veľké Hincovo pleso" in High Tatras, Slovakia. The lake occupies an "overdeepening" carved by flowing ice that once occupied this glacial valley.

The term "geomorphology" was first used in German in 1858 and later became common in English, German, and French. An early model was the "cycle of erosion" developed by William Morris Davis between 1884 and 1899. Davis thought landscapes change in a repeating pattern.

Another model was developed by Walther Penck in the 1920s. Penck believed landforms change through uplift and wear-down processes. Both Davis and Penck tried to make the study of Earth's surface more general and useful worldwide.

Climatic geomorphology

As explorers traveled the world in the late 19th century, they noticed climate seemed to affect landforms. Early work by Wladimir Köppen, Vasily Dokuchaev, and Andreas Schimper helped start this idea. Davis also recognized climate's role. But by the mid-20th century, some critics said this field wasn't very strong.

Part of the Great Escarpment in the Drakensberg, southern Africa. This landscape, with its high altitude plateau being incised into by the steep slopes of the escarpment, was cited by Davis as a classic example of his cycle of erosion.

Quantitative and process geomorphology

In the mid-20th century, scientists began using math and measurements to study landforms more precisely. They looked at rivers, hillslopes, and other features with tools like fluid dynamics and modeling. This helped predict how landscapes change over time.

Contemporary geomorphology

Today, geomorphology studies many different approaches. Researchers now see that landscapes are always changing and that processes don't always lead to the same results. Climate geomorphology still exists, especially with concerns about global warming. The old "cycle of erosion" model is still used in teaching, even though it has limits.

Geomorphological Processes

Geomorphological processes include how loose material is created by weathering and erosion, how this material moves, and where it ends up. Key processes that shape the Earth’s surface involve wind, waves, chemical dissolution, mass wasting, groundwater flow, surface water, glacial action, tectonism, and volcanism. Other processes include those influenced by cold temperatures, salt, and underwater currents.

Gorge cut by the Indus River into bedrock, Nanga Parbat region, Pakistan. This is the deepest river canyon in the world. Nanga Parbat itself, the world's 9th highest mountain, is seen in the background.

Aeolian processes describe how winds shape the Earth. Winds can wear away, move, and drop materials, especially in dry places like deserts where there is little vegetation and lots of fine particles.

Living things also affect the shape of the land through biogeomorphologic processes. Plants and animals can change how rocks break down, move soil, and even affect how much erosion happens by influencing the climate.

Wind-eroded alcove near Moab, Utah

Main article: Fluvial

See also: Hack's law and Sediment transport

Rivers and streams carry not just water but also bits of rock and soil. The water moves these materials downstream in different ways. Rivers can also wear away rock to create new pieces of sediment. As rivers grow larger by joining together, they form patterns like branching networks. These rivers shape the land in various ways, creating features such as alluvial fans, oxbow lakes, and fluvial terraces.

Beaver dams, as this one in Tierra del Fuego, constitute a specific form of zoogeomorphology, a type of biogeomorphology.

Glaciers may cover limited areas, but they change landscapes greatly. As glaciers move, they scrape and pull rocks, creating fine particles called glacial flour. When glaciers melt, they leave behind piles of rock called moraines. Glacial erosion makes U-shaped valleys, unlike the V-shaped valleys formed by rivers.

Soil, loose material, and rock move down slopes due to gravity through sliding, flowing, or falling. This movement changes the shape of slopes and can happen quickly in areas where the land is shifting.

Seif and barchan dunes in the Hellespontus region on the surface of Mars. Dunes are mobile landforms formed by the transport of large volumes of sand by wind.

Both volcanic and deep Earth processes can reshape landscapes. Volcanoes cover old land with new material and create new shapes. Deep processes can lift or lower the Earth's surface.

Overlap with other fields

Geomorphology shares ideas with many other areas of study. For example, the way rocks break down over time, called weathering, is important for both geomorphology and for soil scientists and chemists. Engineers who work with water and the land, like those who design canals or study slope stability, also need to understand how land changes shape. Glaciology, the study of glaciers, helps explain how glaciers shape the land, especially in cold areas. All these fields work together to help us understand how Earth’s surface changes.