BIOTURBATION - How Plants and Animals Change the Surface of the Planet - Bioturbation aids the penetration of air and water and loosens sediment to promote winnowing or washing (transportation). Bioturbation is the disturbance of the soil or sediment by living things. It may include displacing soil by plant roots, digging by burrowing animals (such as ants or rodents), pushing sediment aside (such as in animal tracks), or eating and excreting sediment, as earthworms do. Earthworms digging through soil can shift older materials to higher layers. They can also leave behind traces of their activity in the form of fecal matter which, over time, lithifies. Burrowing marine animals such as crabs, clams, and shrimp, can radically change sedimentary layers. These animals burrow into the sand, creating tunnels and moving materials from one sedimentary layer to another. If the tunnels are sturdy enough, they may later be filled with material formed at a later time. Tree roots often run through multiple layers of soil. As they grow, they may disturb or mix sediments. When they fall, they pull older materials to the surface.

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Bioturbation

How Plants and Animals Change the Surface of the Planet

by Andrew Alden 

One of the agents of organic weathering, bioturbation is the disturbance of the soil or sediment by living things.

It may include displacing soil by plant roots, digging by burrowing animals (such as ants or rodents), pushing sediment aside (such as in animal tracks), or eating and excreting sediment, as earthworms do.

Bioturbation aids the penetration of air and water and loosens sediment to promote winnowing or washing (transportation).

How Bioturbation Works

Under ideal circumstances, sedimentary rock is formed in predictable layers.

Sediments -- bits of soil, rock, and organic matter -- collect on the surface of the land or at the bottom of rivers and oceans.

Over time, these sediments are compressed to the point of which they form rock. This process is called lithification.

Layers of sedimentary rock may be seen in many geological structures.

Geologists are able to determine the age and composition of sedimentary rock based on the materials included in the sediment and the level at which the rock lies.

In general, older layers of sedimentary rocks lie under newer layers. Organic matter and fossils that make up the sediments also provide clues to the age of the rock.

Natural processes can disturb the regular layering of sedimentary rock.

Volcanoes and earthquakes can disturb layers by forcing older rock closer to the surface and newer rock deeper into the Earth. But it doesn't take a powerful tectonic event to disturb sedimentary layers.

Organisms and plants are constantly shifting and changing Earth's sediments. Burrowing animals and the actions of plant roots are two sources of bioturbation.

Since bioturbation is so common, sedimentary rocks are divided into three groups that describe their level of bioturbation:

·  Burrowed rock is filled with evidence of organisms, and may contain elements from several different sedimentary layers.

·  Laminated rock shows evidence of bioturbation at the surface caused by non-burrowing activity. Examples include furrows and tracks created by aquatic or terrestrial animals.

·  The massive rock contains sediments from just a single layer.

Examples of Bioturbation 

Bioturbation occurs in many different environments and at several different levels. For example:

·  Earthworms digging through soil can shift older materials to higher layers. They can also leave behind traces of their activity in the form of fecal matter which, over time, lithifies.

·  Burrowing marine animals such as crabs, clams, and shrimp, can radically change sedimentary layers. These animals burrow into the sand, creating tunnels and moving materials from one sedimentary layer to another. If the tunnels are sturdy enough, they may later be filled with material formed at a later time.

·  Tree roots often run through multiple layers of soil. As they grow, they may disturb or mix sediments. When they fall, they pull older materials to the surface.

Significance of Bioturbation

Bioturbation provides researchers with information about sediments, and thus about the geology and history of the sediments and the area. For example:

·  Bioturbation can suggest that a particular area is likely to be rich in petroleum or other natural resources;

·  Bioturbation can provide clues to ancient life in the form of fossilized animal and plant remains;

·  Bioturbation can provide information about life cycles, dietary habits, and migration patterns of contemporary organisms.

Andrew Alden

Introduction

Professional geologist, writer, photographer, and geological tour guide

Thirty-seven years of experience writing about geological subjects

Six years as a research guide with U.S. Geological Survey (USGS)

Member of Geological Society of America (GSA), and American Geophysical Union (AGU)

Experience

Andrew Alden is a former writer for ThoughtCo who contributed hundreds of articles for more than 17 years. Andrew works as a geologist, writer, editor, and photographer. He has written on geological subjects since 1981 and participates actively in his field. For example, Andrew spent six years as a research guide with the U.S. Geological Survey, leading excursions on both land land and at sea. And since 1992, he has hosted the earthquakes conference for the online discussion platform, The Well, which began as a dialogue between the writers and readers of the Whole Earth Review.

In addition, Andrew is a longtime member of the member of the Geological Society of America — an international society that serves members in academia, government, and industry; and the American Geophysical Union — a community of earth and space scientists that advances the power of science to ensure a sustainable future.

Andrew lives in Oakland, California; and though he writes about the whole planet and beyond, Andrew finds his own city full of interest too and blogs about its geology.

Education

Andrew Alden holds a bachelor's (B.A.) degree in Earth Science from the University of New Hampshire, College of Engineering and Physical Sciences, in Durham, N.H.

Awards and Publications

Andrew Alden on Earthquakes ​(The Well Group, Inc., 2011)

Assessment of River — Floodplain Aquifer Interactions (Environmental and Engineering Geoscience, 1997)

Andrew Alden on Hosting (The Well Group, Inc., 1995)

ThoughtCo and Dotdash

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https://www.thoughtco.com/what-is-bioturbation-1440851