Morphoclimatic systems

A  (MS) is a set of external geological actions that shape landforms in a particular zone. It depends on factors such as climate, lithology... but also on the specific actions of the human being.

• Climate: external agents that characterize an specific area and its geomorphogenetic actions.
• Lithology: part of the geology that studies the rocks (colour, texture, grain size, or composition). Rocks influence the landscape of a particular area. Cohesion, permeability and changeability are rock features that need to be taken into account.

 Type of morphoclimatic systems are glaciers, periglacial areas, deserts and humid zones.

Sedimentation

Sedimentation is the process by which materials are deposited in places where agents lose strength

It can be:

• Deposit: the materials are composed of solid particles
• Precipitation: the materials are dissolved and are deposited according to pressure, temperature…

Sediments are settled horizontally (horizontality principle), with those on the top being the more recent (superposition principle).

Sedimentation is influenced by factors such as climate, topography... Dunes are a good example of this.

Transport

Transport is the movement of materials from one place to another thanks to the external geological agents.

It can be:

• Selective: The transfer depends on the size of the materials and the energy of the agents (wind and water).

• Rivers can transfer solid materials in different ways:

• Flotation: The less dense materials.
• Suspension: Equal density of water or a similar one.
• Saltation: It´s not a continous flow. The water will push the materials.
• Dissolution: The material dissolves and when the water disappears, it precipitates.
• Rolling or sweeping along: When it´s a round material

• Wind: Its transport ability is much lower than water, but in suspension it can transfer materials in big distances and spread them much further than water.

• Non-selective: Transport does not depend on materials sizes.

• Ice (glacier): Doesn´t allowed the materials touch the ground so everything is transport with the same speed, and when the ice melts, everything is deposited in the same way.

• Water (torrents): When the water strength is very big there´s no difference in size.

Erosion

Erosion is the process that produce the wearing away of rocks because of the action of the geological external agents (wind, water...)

Different factors may influence the erosion process:

• Steepness of the slope: In steep slopes, the materials are less stable. If there isn´t any vegetation, the water takes away the superficial layers of soil so organic materials that can regenerate the vegetation are removed
• Weight of the sediments.
• Cohesion: Internal connection of the rock components. Depends on:
• Degree of fracture of the material
• If the rock is soft or has been weathered previously (less cohesion).
• Presence or absence of water.
• Presence or absence of plastic materials.
• Absence of vegetation: The roots are support factors. They hold the land. The aerial part of the plants filtrate the rainwater so it falls slowly.
• Climatic factors: Erosion is stronger in windy/rainfall areas

Erosion types:

• Leakage: abrupt drops of loose rocks. The acting agent here is the gravity.

• Landslides: they are huge leakages.
• Slippery: The land slips over a take-off surface.

• Flows and tracks: mud rivers.

• Creeping: When the volume of a plastic land increases (humid variety) because of the level of water a molecule goes up but when the land dehydrates, that molecule goes down (small waving).

• Gully: Channels or cracks formed on plastic material slopes because of the rainfall.  As a result of these processes hoodoos or fairy chimneys are formed. These are pyramidal structures with a rock of a different and more resistant material on the top of them.

Weathering

Weathering is the process of disintegration and transformation of the rock into the different minerals that form it. 

It can be:

• Physical or mechanical: refers to the occurrence of fractures and the fragmentation into rock pieces increasingly smaller that preserve the properties of the original material. It usually takes place in extreme climates.

• Frost weathering: The water is deposited in the cracks. During night that water gets frozen because of the frosts, and it increases its volume, breaking that way the stone.
• Haloclasty: Disintegration of rocks caused when saline solutions inside rock cracks evaporate, leaving salt crystals behind (dry places). Salt ruins materials and descompones rocks because of its corrosive action.
• Thermal stress:  results from expansion and contraction of rocks, due to temperature changes. Not all materials expands and contracts equally: dark areas get warmer and create tensions between the different materials of the rock.
• Biological: A simple tree has a lot of strength. It is capable of breaking the rocks as it´s growing in between them.
• Animals like rabbits and badgers dig tunnels on the floor which produces a lot of weathering.

• Chemical: Different chemical processes may alter the rocks chemical composition. These processes need water (universal solvent), so they happen in humid areas.

• Dissolution: water dissolves the rocks. There are processes of carbonation (calcium hydroxide reacts with carbon dioxide and forms insoluble calcium carbonate) and decarbonation
• Hydration: different volume and behavior with a dehydrated material (for example, clay). Hydration produces contraction cracks and dehydration, retraction cracks.
• Oxidation: Combination of materials with Oxygen. There are differences between metals and not metallic materials. For example, ochre color appears when Roussillon is mixed with Oxygen.
• Biological: For instance, lichens. They produce chemical substances that gradually dissolve the rocks. Then, organic material is formed. Other living organisms produce ammonia, we (human beings) produce CO2 and so on.

What is Geomorphology?

Geomorphology is a part of the geology that studies the relief, which is the combination of the geographic accidents that we can see on the Earth surface. The landscape is how the relief looks like, the surface aspect.

This is a dynamic element, that is constantly changing as a result of the uninterrupted intervention of the processes that form (internal geological processes) and model (external processes) the relief.

Geomorphology studies the relief from the shape point of view (geometry). Over the years, there have been many different theories and ideas about how the relief was formed:

• Catastrophism: This theory proposes that the Earth has been affected in the past by sudden violent events when the big chains have been formed. These kind of changes weren´t continous (for example, the universal deluge). George Cuvier, a French naturalist and zoologist, became the most influential proponent of Catastrophism in geology in the early years of  the 19th century.
• Gradualism: This theory contrasts the catastrophism. It holds that the changes are the result of slow and continous processes. We should be able to see this phenomenons nowadays since they must occur gradually. This theory was later included into Charles Lyell´s theory.

Next entries will deal with the different aspects related to the agents and processes that provoke these changes.

Introducing this blog

This blog is devoted to discuss all aspects of Geomorphology that have been studied previously in class (Escuelas Pías, Albacete, 4º ESO).

Comments to each entry are welcome.