Periglacial Mophological Systems

A Periglacial MS is an area in the edge of a glacial system, formed also because of the effect of ice, but due to freezing and unfreezing processes (areas with temperatures ranging 0-10º)

The typical landscapes are:

• Patterned ground, formed by symmetrical geometric shapes of ground material

• Blockfields, or areas covered by large angular blocks.

• Permafrost:  soil at or below the freezing point of water 0 °C

• Padded grass: grass growing in a frozen area that increase its volume due to ice and looks like padded when unfreezing

Glacial Mophological Systems (Glaciers)

A Glacial MS (glacier) is a zone where a huge amount of snow is accumulated creating areas of permanet ice (areas of high lattitude or altitude). This accumulation flows down, draging sediments, to areas with higher temperature, where it melts.

There are different types:

• Alpine (mountain, valley) glacier: A glacier head (cirque) is formed in high altitude areas and the glacier flows downhill (like an ice river)

• Continental glacier (ice sheet): Large extensions of ice in high lattitude areas.

• Hanging glaciers: Similar to alpine glaciers but smaller, running at a different level and ending on a bigger one.

A mountain glacier has different parts:

• Cirque: wide place on the top where snow is accumulated

• Tongue: ice river that flows downhill

• Moraine: mass of rocks dragged by the ice in its way down the mountain. Moraines can be:
• Lateral. Formed on the sides of the glaciar.
• Rogen. Under the ice, in touch with the ground.
• Medial moraine. Union of lateral moraines in the confluence of two glaciers.
• End or terminal. It´s formed where the glacier melts 

Some geological effects associated to a glacier are:

• Crevasse: fracture zone in a glacier

• Serac: huge block or column of ice

The glacier shapes the land relief in several ways:

• Glacial erratic: piece of rock that differs from the size and type of rocks that are native to the area in which it rests

• Sheepback rock: result of the glacier erosion (abrasion) process

• Glacial till: piles of glacial deposits of different types

• Esker: Long, sinuous glacial deposits

• Drumlin: hill formed by the sediments draged by the glacial ice

• Tarn (ibón in the Pyrenees): lake formed in when the glacier finds a basin.

• Horn: mountain with a pyramidal shape eroded by different glaciers.

• Glacier valley: U-shaped valley with steep walls formed by glacial erosion.

• Hanging valleys: They are those that flow at a different height than the principal, and this one cut its walls.

• Fiord: glacier valley filled of sea water

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.