The Earth´s relief

THE STRUCTURE OF THE EARTH

Upper mantle and crust form the LITHOSPHERE

Continental Drift Theory (By Alfred Wegener)Millions of years ago there was only one continent called Pangaea

What are Tectonic Plates?

• The Earth’s crust is divided into large blocks called plates. The heat inside the Earth creates currents which move the plates around.

• Oceanic plates carry the oceans.

• Continental plates carry the continents.

The movement of plates is called Plate Tectonics

Plates on the Lithosphere

The Earth’s major plates and plate boundaries

Las placas tectónicas : divergencia y convergencia

What happens where plates meet?

• The places where plates meet are called plate margins or boundaries. It is often in these places that the Earth is unstable resulting in earthquakes and volcanoes.

We can find three main zones •The “Ring of Fire” is a boundary area around the Pacific Plate, which affects the coastal areas of Asia, western America and Oceania. •The mediterranian-asian area, which affects the Mediterranean Sea, the Himalaya and Indonesia.•Mid-Ocean ridges which result from divergent plates separating from each otherand creating new crust.

What are the different types of plate margins (boundaries)?

Boundaries between tectonic plates can be of three types. Click on the links to view animations of each plate boundary.

1. Constructive plate boundaries create new crust, and often give rise to volcanoes and earthquakes.

2. Destructive plate boundaries create mountains and may give rise to volcanoes and earthquakes.

3. Conservative plate boundaries do not create or destroy land, but often give rise to earthquakes (not volcanoes).

Key Words

Oceanic

Continental

Friction

Earthquakes

Magma

Volcanoes

Subuction

Fold Mountains

VIDEO

Las dorsales oceánicas

CONTINENTS AND OCEANS

Earth´s crust

Continents (emerged land)Represent 30% of Earth´s surface

Oceans(submerged land)Represent 70% of Earth´s surface

Oceans

Continents

Extension

CONTINENTS AND OCEANS

Plain

Peak

Continental Relief: Mountains

• Are high landforms with steep sides. The world´s highest mountain range is the Himalaya in Asia.

• Rocky Mountains, Canada

ALPS : example of young mountains which are high and their peaks are very prominent

SIERRA MORENA : example of old mountains which are low and rounded because of erosion

Shields or platform (escudos y penillanuras) are ancient mountains ranges that have eroded and become plains or small rounded hills

Continental Relief : valleys

• Are areas of low land between mountains. Rivers flow through many valleys.

• Valley of Pas, Asturias

Continental Relief : plateaus

• Are large, raised plains. The highest plateaus are in Tibet in Asia, and in Bolivia in South America

Continental Relief: plain

• Are low, flat areas of land. Large plains are often found on the coasts, and are formed by large rivers.

Continental Relief: Basins

• Are natural depression or low areas of land. Some are below sea level.

DUTCH POLDERS

DeltaLagoon

Archipelago

Bay

Isthmus

Peninsula

Ria

Cliff

GulfCape

Beach

Peninsula: is an area of land surrounded by water on all sides except one. Isthmus connects a peninsula to a continent.

Coastal Relief:Capes and Gulfs

Cape or headland is a part of the coast which extends into the sea

Gulf: Is a large area of a sea or ocean partially enclosed by land. A bay is a small gulf.

Video http://blip.tv/geobytes/coastal-erosion-features-351185

Coastal Relief: Cliffs

• Are steep rock formations in high coastal areas

• Falaise d´Aval, Haute Normandie.

CLIFFS AND WAVE-CUT PLATFORMSCliffs are steep rock faces along the coastline, they tend to form along coastlines with resistant rocks parallel to the coast.

Coastal Relief: Islands

• Are areas of land surrounded by water on all sides. A group of islands is called an archipelago

Fjords

• Are a long, narrow inlets with steep sides or cliffs, created by glacial erosion.

Fiordos noruegos

Galician Sea inlets

• Sea inlets (ría) – are drowned river valleys

Lagoon (albufera)

• Small lake separated to the sea by a bar of sand.

Beaches are the main feature of deposition found at the coast.

BEACHES

Beaches are the accumulation of sand in flat coastal areas

OCEANIC RELIEF

CONTINENTAL WATERS

Rivers

Drainage Basins have a number of distinct features:

•The edge of a drainage basin is characterised by the highest points of land around the river, this is known as the watershed (cuenca fluvial or cuenca hidrográfica).

•The point at which a river starts is called its source. •As the river continues to flow down stream it may be joined by smaller rivers called tributaries. •The point at which these smaller rivers join the main river is known as a confluence. •As the river continues its journey, eventually reaches the sea - the point where the river flows into the sea is known as the river mouth.

Watershedhttp://techalive.mtu.edu/meec/demo/Watershed.html

RIVER´S LONG PROFILE

Upper CourseUpper Course Middle CourseMiddle Course Lower courseLower course

SOURCESOURCE

MOUTHMOUTH

Course Gradient Valley and channel shape Cross profile

Upper Steep Narrow, shallow channel V-shaped valley, steep sides, canyons, waterfalls.

Middle Medium Wider, deeper channel Gently sloping valley sides, meanders.

Lower Gentle Very wide, deep channel Very wide, almost flat valley, deltas, estuaries.

HIG

H C

OU

RS

EM

IDD

LE C

OU

RS

ELO

W

CO

UR

SE

Rivers tear away materials

Landforms at the upper course of a riverhttp://www.cleo.net.uk/resources/displayframe.php?src=308/consultants_resources%2F_files%2Fintespur2.swf

V-shaped Valley - a valley which resembles a 'v' in cross section. These valleys have steep sloping sides and narrow bottoms.

Waterfall - Waterfalls usually occur where a band of hard rock lies next to soft rock.They end up creating steep sided valleys known as gorges or canyons.

http://www.cleo.net.uk/resources/displayframe.php?src=307/consultants_resources%2F_files%2Fgorge.swf

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1305/es1305page01.cfm?chapter_no=visualization

Landforms at the upper course of a river

•Here the river channel has become much wider and deeper as the channel has been eroded and the river has been fed by many tributaries upstream.

•As well as changes in the river channel, its surrounding valley has also become wider and flatter in cross-section with a more extensive floodplain.

•Unlike the relatively straight channel of the upper course, in the middle course there are many meanders (bends) in the river.

Landforms at the middle course of a river

Over time meanders gradually change shape and migrate across the floodplain.

Meander Formation

As a river continues its journey towards the sea, the valley cross section continues to become wider and flatter with an extensive floodplain either side of the channel.

Floodplains

Features in the lower course of a river

When the river floods over the surrounding land it loses energy and deposition of its suspended load occurs. Regular flooding results in the building up of layers of nutrient rich alluvium which forms a flat and fertile floodplain

Features in the lower course of a river

Deltas Deltas are found at the mouth of large rivers - for example, the Nile, Ebrus or Mississippi. A delta is formed when the river deposits its material faster than the sea can remove it.

Estuary A partially enclosed body of water along the coast where freshwater from rivers and streams meets and mixes with salt water from the ocean.

Delta

Rivers as hazards

Floods have some serious impacts

People are killed by flood waters, buildings are damaged or destroyed and jobs are lost because of damage to premises and equipment

The effects of flooding are worse in poorer countries than richer countries because there´s less money to spend on flood protection and to help people after a flood.

Flooding in Boscastle, UK (2004) Flooding in Bangladesh (1998)

MAIN CAUSES OF RIVER FLOODING

Physical factors: Prolonged rainfall

Heavy rainfall

Snowmelt

Type of soil

Human factors:

Impermeable rocks (clay) – water doesn´t percolate into the rock, but flows over the surface

Deforestation

Building Construction

A flood occurs when a river bursts its banks and the water spills onto the floodplain.

The ground will become saturated and infiltration will be replaed by surface run-off

Release water

Changes in the land use: •Trees interdept rainfall, reducing the amount of water reaching the river

•Impremeable tarmac and concrete surfaces – infiltration and throughflow are reduced while surface run-off is increased.

Flash flood – There is a lot of run-off; increases the discharge quickly.

Lakes are permanent masses of water which have accumulated inland.

When they are small they are called lagoons.

If their water is salt water they are called inland seas.

The water in lakes has different origins:

• Precipitation: in this case, the volume of water changes from one season to another. •Rivers and groundwater•Glaciers

Caspian Sea

Groundwater runs and is stored under the ground. It represents 25% of the water on the continents.

Most groundwater comes from precipitation. When it rains, some water penetrates the ground and filters through porous rocks.

When it reaches permeable rocks, it cannot pass through and forms aquaifers and underground rivers and lakes.

In limestone areas, water dissolves the rock and creates caves and caverns with stalactites and stalagmites.

Glaciers are large, slow moving, masses of ice, that deform and move downslope under their own weight. They may be considered “rivers of ice”

Approximately 10% of the earth's surface is covered by glaciers. Large areas of glacial ice are found in high latitude areas such as Greenland and Antarctica, however glaciers are also found in areas of high altitude (e.g. the Rockies, Alps, Himalaya).

During the last ice age, glaciers existed in Britain and the last glaciers retreated from Britain and Ireland around 10,000 years ago when the last ice age drew to an end.

http://www.gatm.org.uk/geographyatthemovies/glaciation.swf

Glaciers

Landforms created by glacial erosion:

Cmw Or cirques

•Glacial troughs are steep-sided valleys with flat bottoms. They start off as a V-shaped river valley but change to a U-shape as the glacier erodes the sides and bottom, making it deeper and wider.

V shaped valley formed by river erosion

Glacier

U shaped valley

Landforms resulted from glacial deposition: Morraine

•Glaciers can move material over very large distances. The material is transported in the glacier, on the surface, or pushed in front of it. •When the ice carrying the material melts, the material is dropped on the valley floor – this is called deposition.

Morraine: Are landforms made out of material dropped by a glacier as it melts. It is a mass of unsorted rocks, clays and sands.

•Terminal morraine builds up at the snout (end) of the glacier when it remains stationary. It is deposited in semicircular mounds.

• Recessional morraine

http://www.wwnorton.com/college/geo/egeo2/content/animations/18_1.htmhttp://www4.uwsp.edu/geo/faculty/lemke/glacial_processes/MoraineMovie.html

Long pile of rocky material at the edge of a glacier is called a lateral moraine and one in the middle of the glacier is called a medial moraine. Lateral moraines form at the edges of the glacier as material drops onto the glacier from erosion of the valley walls. Medial moraines form where two glaciers join together. In this case, the lateral moraines from the edges of each glacier meet in the middle to form the medial moraine.

Landforms resulted from glacial deposition: Morraine

Medial moraine

Lateral moraine

Lateral moraine

Did you know…

70% of Earth´s surface is formed by water. However, only 2,5% is fresh water, that is, can be used for consumption. Most of it is retained in glaciers in the form of ice. Therefore, only a very small proportion of water 0,6% can be used for consumption.

Did you know …

• Water used for consumption has become a scarce resource because:

• World population leads to an increase in water consumption.•Some aquifers are polluted.

Did you know …

Since 1900 world population has been doubled, but water consumption has grown 6 folds due to improvemtns in standards of living

Did you know …

Today, almost 40% of world´s population have to face severe problems related to water (shortage, contamination…)

Shortage and lack of water in the world

Uses of waterAgriculture is the economic activity with highest water consumptions.

In Spain, 80% of water available for consumption will be used in crop fields. It is therefore necessary to improve irrigated technologies in order to avoid leakages in canals, as well as taking certain measures like not using water during the hottest times of the day.

Uses of water

In reservoirs, water from rivers will be stored. Also, we build dams and hydroelectrical power stations in rivers to produce electricity.

Very often, water from rivers and lakes are treated in water plants before its consumption.

Uses of water

Rivers are used to transport people and goods from one place to another, becoming very effective means of communication

Uses of water

Rivers and lakes attract tourism, because they offer a beaituful scenery and the opportunity to practice many sports in contact with nature. Tourism creates many jobs in these areas.

DESTRUCTION OF THE LANDSCAPE BY HUMAN ACTION

Mining

Deforestation

Coastal urbanization

Living with tectonic hazards

What are earthquakes and volcanoes?

Earthquakes• Occur when plates are

moving towards or alongside each other e.g. the conservative plate margin at the San Andreas Fault in California, USA

• Pressure build up until there is a sudden movement, sending a shockwave through the Earth’s crust

• Focus – point where the shockwaves start

• Epicentre – the point above the focus on the Earth’s surface

Volcanoes• Form when semi-molten

rock (magma) rises to the Earth’s surface. When the magma reaches the Earth’s surface it becomes lava.

Vibrations during an earthquake are measure using a seismometer this produces a seismograph.

The Richter scale measure the energy released on a scale of 1 to 10.

http://environment.nationalgeographic.com/environment/natural-disasters/forces-of-nature/?section=v

Another page: http://news.bbc.co.uk/2/hi/science/nature/4972366.stm

Why do effects of tectonic hazards vary?

The effects of tectonichazards vary because

1. Some places are nearer to the source of earthquakes or volcanoes

2. Some places are better prepared than others

3. Some places have more resources to deal with the effects of the hazard

Primary effects

Immediate effects

•Death/injury

•Loss of land/buildings

•Damage to infrastructure

Secondary effects

Longer term effects

•Lack of shelter

•Poor water/food supply

•Loss of income

•Long-term damage to infrastructure

Kobe Earthquake - JapanMEDC

Gujarat Earthquake - IndiaLEDC

You may be asked to compare impacts between

MEDCs and LEDCs

Why do people live in hazardous areas?

• People feel that it “won’t happen to them” and that they are well prepared

• Some areas like California (USA), have an excellent climate, superb beaches and a wide range of job opportunities

• In places like Iceland, geothermal energy can be generated from the volcanic rocks

• Many minerals and precious stones are found in volcanic areas

• Volcanic rock provide mineral-rich fertile soil, which is excellent for agriculture

• Volcanic soil is often found in spectacular areas of scenery which provide an excellent opportunity for the development of tourism.

Living with Tectonic Hazards

How can the risk of tectonic activity be reduced?

Preparing for Earthquakes

• It is very difficult if not impossible to predict earthquakes• Therefore it is more worthwhile to invest money and resources in

preparing for earthquakes• MEDCs tend to prepare better for earthquakes than LEDCs

Predicting Volcanic Eruptions

As a volcano becomes active, it gives off a number of warning signs. These warning signs are picked up by volcanologists (those who study volcanoes) and the volcano is monitored.

Preparing for Volcanic Eruptions

A detailed plan is needed for dealing with a possible eruption. Everyone who could be affected by the eruption needs to

know the plan and what they should do if it needs to be put into action.

•Planning for a volcano includes creating an exclusion zone around the volcano •Being ready and able to evacuate residents •Having an emergency supply of basic provisions such as food •Funds need to be available to deal with the emergency and a good communication system needs to be in place

How to prepare?

Why are the effects of hazards worse in LEDCs than MEDCs?