Amazon Notes FQ 1 & 2 - NIS Geography



Amazon Notes FQ 1 & 2

FQ 1 What are the elements that make up a natural landscape?

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Where are Tropical Rainforests located and why are they there?

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▪ The name rain forest was first used at the end of the 19th Century to describe forests that grow in constantly wet conditions

▪ Today, scientists define rain forests as forests that receive more than 2,000 mm of rain evenly spread throughout the year

▪ A rainforest is often referred to as a jungle, which is a Hindi word from India meaning a wilderness

▪ Tropical rain forests are found in a belt around the equator, where temperatures and rainfall are very high all year round

▪ There is very little variation between the seasons

▪ They will have an even distribution of rainfall annually

▪ Warm temperatures with less variation during the year

▪ The best known rain forests are found in tropical regions between the Tropics of cancer and Capricorn

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▪ One of the most well known rainforests is the Amazon

▪ The Amazon is in South America

▪ The Amazon rainforest is the largest rainforest in the world

▪ It covers an area about two thirds the size of the US

▪ Two thirds of the Earth’s fresh water can be found there

▪ The Amazon was given its name by European explorers, after a tribe of fierce women called Amazons

▪ Whether this tribe really existed is one of the many mysteries of the jungle

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Tasks

Locate and name on a world map provided the world’s tropical rainforests

Use the table to locate these regions

|Latitude & longitude Table | |

|Latitude & longitude |Region |

|18N to 10N |Eastern half of Central America |

| |Zaire Basin |

| |East & west coast of India |

|10N to 10S |West coast South America |

|5S to Tropic of Capricorn |Andes Mountains to east coast Brazil |

|10W to 10E |Coast of Gulf of Guinea |

|Hervey Bay |North-east coast of Australia |

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| | |

Using an atlas for reference, construct a star diagram that shows the various features that tropical rainforests have in common.

• location on the globe

• relief

• rainfall

• temperature

• nearness to the sea

Other areas of the world share these same location factors. Suggest why these do not have tropical rainforests.

What is the most important factor causing the location of tropical rainforests?

Geographic Description

Amazonia, the region of the Amazon and its tributary rivers, is the largest tropical rainforest in the world

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Originally two million square miles of the region was coved with dense tropical forest. Its vastness and inaccessibility have protected the forest. 30 years ago government sponsored road building projects, colonization schemes and industrial developments have changed the forest to polluted factory sites and sprawling unplanned settlements.

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The River

The Amazon is the largest of the world’s rivers in terms of volume of water discharged. The network of river channels covers most of the northern part of the South American continent. The main river is 6,600km long. The catchment is 11,064,480 square kilometers, the same size as the USA.

The Amazon carries a phenomenal amount of sediment to the ocean each day. Equivalent to 4,200 truck loads per day. It is deep enough for ocean going vessels to travel to Manaus over 1,500km up the river.

|Features |Amazon River |Waikato River |

|Length |7,200km |425km |

|Catchment area |5.7m km2 |14,258km2 |

|Discharge |160,000m3 |360m3 per second |

|Daily suspended load |1.3 tons |500 tons |

|Width at mouth |100m deep 70km wide |3.5-7m deep |

| | |700 meters wide |

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The discharge is so great that it noticeably dilutes the salinity of the Atlantic's waters for more than 100 miles offshore.

The River

The Amazon River is fed by more than 1,000 tributaries, including seven that are more than 1600 kilometres long, and it drains more than half of Brazil, as well as parts of Bolivia, Peru, Ecuador, Colombia and Venezuela.

Its total drainage basin of some 7,000,000 square kilometres and encompasses about one-third of South America, an area more than 10 times the size of Texas and nearly as large as the entire contiguous United States.

Over most of this vast region the climate is very warm and humid. Rain falls about 200 days each year, and total rainfall exceeds 2 metres per year. One result of so much rain is that Amazonia is covered by the largest tropical rain forest in the world.

As the fresh water leaves the Amazon River mouth it carries out with it, enough nutrients to feed fish communities as far away as Newfoundland Banks, off of Canada.

The head waters of the Amazon begin in the mountainous regions of the Andes, cascading down small streams, joining together to form major rivers such as the Medera.

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Crossing the interior basin of Brazil, the river flows very sluggishly, and becomes braided into many channels. Beyond the river banks are broad swampy flood plains dotted with lakes and covered with seasonally flooded forests.

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The River Basin:

The Amazon flows along a very gentle gradient at only about 5cm per kilometre. It branches into numerous secondary channels, which are separated by very densely forested islands.

All along the course of the river there are seasonal floods.

Tributaries flowing from the south tend to reach their highest stages from February to April, while those coming from the north tend to crest in June and July.

The Amazon also varies in colour. Some of its tributaries are called "white" rivers, through their colour is more often a murky yellow or tan. Others are known as "black" rivers, their waters dark but crystal clear.

The white rivers rise in the Andes, and their turbidity results from the heavy loads of mud and silt they carry.

The black rivers, in contrast, rise in areas of ancient basement rock where little sediment remains to be washed away; only dissolved organic matter stains their clarity.

For many miles the black and white waters flow side by side in separate, clearly defined streams before they finally intermingle.

About 600 miles from the coast, at Obidos, the ocean begins to affect the river. Tides are able to penetrate this far upstream because of the extremely gentle slope of the land.

From November through May the volume of the mainstream swells. For example, on June 1, 1989, the level of the river at Manaus, 900 miles from the ocean, had been 45 feet above low water, nearly reaching the 1953 all-time high-water mark on the flood gauge.

The Amazon's volume in that month far exceeded the combined flow of the next eight largest rivers on Earth, as it does by the end of every May, even in years of normal flow.

During the second half of the year, the flow diminishes. In November 1990, around Manaus, stretches of white beaches and sandbars were exposed to the sun for the first time in living memory. The river had fallen 50 feet to its lowest level on record in this century.

The only official fluviometric studies of the main stream flow were done in 1963 and 1964 (years estimated of lesser than average rainfall) by the U.S. Geological Survey. Measurements were made at Obidos, 960 kilometres inland, where the Amazon squeezes through a single channel little more than a mile wide.

Findings gave the average minimum discharge at 340000 cumecs (cubic metres per second) while the average maximum reached 940000 cumecs. For comparison, the Mississippi at Vicksburg averages 69,000 cumecs.

It has been suggested that the Amazon's average annual discharge equals 20 percent of the total continental runoff of all rivers on Earth.

There are a few sizable cities along the river's banks and scattered settlements inland, Amazonia is largely uninhabited.

Plantations have been cleared in the jungles, and natives ply the streams in search of latex and Brazil nuts.

Flora and Fauna

The flora and fauna of Amazonia are not all known to science, since so much of them are native to the least explored parts of the rain forest.

No one knows exactly how many species of fish there are in this river-sea, with estimates reported of more than 2,000.

Among these are some of the biggest fish outside the ocean. (The arapaima reaches 5 metres in length and can weigh as much as 180 kilograms.)

Here, too, is the electric eel and the notorious piranha. And the biggest of all snakes, the anaconda, is at home here, more often in the water than out.

The salt sea has contributed many inhabitants to this freshwater sea, including a dolphin, a manatee and stingrays that nestle in the sandbars high up the tributaries where they rush out of the Andes.

Only a tiny percentage of Amazonia's millions of species of plants and animals are known to science, but those few that have been studied have already yielded valuable foods, medicines, and commercial products.

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Vegetation

With fertile conditions, vegetation grows rapidly, aided by the rapid rotting, decomposition, which forms a rich humus layer. This is further encouraged by the wet and warm conditions.

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There is so much competition for sunlight that the forest has become stratified into layers.

The trees that need sunlight the make up the canopy

Other plants use these trees to grown on to get to the sunlight.

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Tasks

Describe the location of the different forest types in the Amazon Basin

What is stratification and how does it work?

Explain the location of these forest types using relief, climate and soils

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Climate

Rainfall and temperature play a large part in determining what the Amazon basin is like.

Over most of this vast region the climate is very warm and humid.

Closeness to the equator ensures high temperatures all year

Heat generates a regular transpiration rainfall cycle. This provides a constant source of water to replenish rainforest growth.

Rain falls about 200 days each year, and total rainfall exceeds 2 metres per year.

One result of so much rain is that Amazonia is covered by the largest tropical rain forest in the world.

Another result is that the river carries by far the largest volume of water of any river in the world. On the average, some 112 billion litres per minute (6 billion cumecs) flow into the sea, about 10 times the flow of the Mississippi. The discharge is so great that it noticeably dilutes the salinity of the Atlantic's waters for more than 100 miles offshore.

Rainfall occurs in the Amazon Basin regularly through three main types

• Orographic rainfall – rain caused by moisture laden air being forced up over the Andes mountains

• Frontal rain – rain caused y warm air laden with moisture being forced up by colder air pushing under it

• Convectional rain – rain generated by heating of the air near to the ground, which picks up moisture and rises quickly, first forming clouds then condensing into rain drops

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The process of convectional rainfall is the most important rainfall in the Amazon. The directions of the wind and small ranges of mountains in southern Brazil mean that little Orographic rainfall occurs in the Amazon Basin.

Tasks

1. Construct a cycle diagram showing the water cycle from the ocean.

2. Why does being near the equator mean a high level of evapo transpiration?

3. How does a high level of evapotranspiration affect the climate?

4. Describe the causes of Orographic rain, frontal rain and convectional rainfall.

5. Why would the Amazon basin get mainly convectional rain?

|Brazil - Manaus Region |

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The Inter Tropic Convergence Zone (ITCZ)

Bands of converging winds and low pressure systems make up the Inter Tropic Convergence Zone. It is the source of most of the Amazon’s rainfall. It moves south from the equator to the southern edge of Amazon and returns north during a nine month period.

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Tasks

1. Write a definition of the ITCZ, including where it is, where it moves to and how it causes rainfall.

2. Why does the Amazon basin have a rainy season twice as long as other rainforest areas

3. Draw a systems model of the ITCZ with inputs, throughputs, outputs and feedback.

4. What is the relationship between the overhead sun and the movement of the ITCZ.

Soils

Soils are formed as a result of a combination of material from different sources

• parent material – alluvium

• dead trees, branches and leaves

• dead insects, birds and other animals

The warm, wet environment causes various ingredients to decompose or rot rapidly and transform into a thin fertile layer of humus

The large volume of rainfall causes many of the acid chemicals in the humus layer to filter the alluvium below. These acids dissolve minerals from the alluvial material; eventually this acidic mix reaches water ways and rivers. This stains the river dark brown and looks like tea.

All fertility is in a shallow layer near the surface. Trees and plants do not grow deeps roots, so for stability trees grow buttresses and link together for support.

Terra Firme – highlands in the Amazon that do not flood

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Soil Systems model for the Amazon Basin

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Varzea – low lying land that receives annual flooding

• The Varzea is the flood plain of the Amazon River.

• Large annual floods cover much of this part of the Amazon basin for months, at least twice a year.

• It is the fertile region that is often occupied and farmed for short term crops between floods.

• Each flood deposits new alluvium on the Varzea and the alluvium provide new material to enhance fertility

•

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Vegetation Process

Competition for space, water and light are the driving factors of vegetation processes in the Amazon rainforest. Competition for light has resulted in a stratified rainforest.

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Orographic zone – reflected, or transmitted light.

A. Canopy, the trees of this layer are like umbrellas with slender trunks and broad canopies.

B. Home of most tropical birds and animals.

C. Densest layer composed of the canopy and tops of smaller tree waiting to break through to the sunlight.

D. Shrubs and treelets

E. Herbs, ferns and saplings

Rainfall

Trees grow towards sunlight. Water flows down. 85-90% of rain that falls on the canopy reaches the ground. It arrives at the soil over lapsed periods of time.

Task

1. What is the relationship between sunlight and stratification?

2. How does stratification influence water dispersal in the forest?

3. Explain the relationship between rainfall and leaching.

4. AMAZON SETTING

Interactions

Climate → Soil: Climate provides soil moisture and leads to leaching of nutrients from soil and parent material.

Soil → Climate: Minimal effects on climate. Vegetation recycles soil moisture through evapotranspiration.

Climate → Vegetation: Where the ITCZ supplies long and regular rainfall, the vegetation is Tropical Rainforest. In the Northern and Southern regions, different amounts of rainfall lead to a variation in the type of vegetation present.

Vegetation → Climate: Evapotranspiration leads to convectional rainfall. When vegetation (forest cover) is removed, there is less rainfall.

Climate → Relief: In areas of high rainfall (orographic type) rates of erosion are higher. This leads to a change in the shape of the land: landslides, riverbank erosion, and deposition on varzea.

Relief → Climate: Orographic rainfall in Brazil’s coastal mountains and further west in the Andes foothills affects local climate and on a broader scale provides more rainfall from the Amazon Basin.

Soil → Vegetation: An increase in soil nutrients leads to an increase in plant growth. Most Amazon soils are nutrient poor, except for varzea and soils derived from volcanic materials.

Vegetation → Soil: The system of nutrient recycling in the humus layer means that rainforest vegetation has evolved through time to grow in poor. Where vegetation is removed, soils are easily eroded.

Soil → Relief: There is a dramatic variation in soils found on different relief features. The soil processes are affected by steepness as well.

Terra firme – poor soil, deeply weathered parent material

Varzea – good soil, new supply of nutrients each year

Andes soil – Steep land, thin soil.

Ancient lake bed – deeply weathered, no nutrients in soil only in humus layer.

Relief → Soils: On steeper land erosion is more important/happens more often and soil is thinner or poorer. On low relief (flatter land) material is deposited and extra nutrients are added.

Vegetation → Relief: When vegetation is removed, bulldozed, burnt, or cut down, the relief can change through increased erosion.

Interactions between Elements of Amazon Basin

|Climate → Soil |Climate - ITCZ |Climate provides soil moisture and leads to leaching of nutrients from soil and parent material creating a soil low in plant nutrients. |

| | |These nutrients end up in streams and watercourses of Amazon Basin. Leads to an increase in the depth and chemical weathering of soils.|

| |Soils - Latosols of the Terra |Minerals containing Iron and Aluminium are concentrated and further lower fertility. |

| |Firme | |

|Climate → Soil |Climate – Orographic rainfall |High amounts of orographic rainfall in the eastern Andes, contributes to seasonal floods in Amazon basin and its tributaries. Soil and |

| |and ITCZ |fine eroded material rich in plant nutrients is carried from the slopes of the Andes to the lower lying Varzea and is deposited. This |

| | |replenishes soil fertility. |

| |Soils – Fertile alluvial Varzea| |

|Climate → Vegetation |Climate – High Temps |High annual temperatures result in the vigorous growth |

| | | |

| |Vege – Tropical Rainforest | |

|Climate → Vegetation |Climate – ITCZ |Where the ITCZ supplies long and regular rainfall, the vegetation is Evergreen Tropical Rainforest. As plants are not stressed, |

| | |flowering and fruiting occur throughout the year. Trees are always in leaf and there is a constant fall of dead leaves to the forest |

| |Vegetation – Evergreen and |floor. The processes of Competition and Stratification occur the most. In the Northern and Southern regions, different amounts of |

| |seasonal Tropical Rainforest |rainfall lead to a water deficit and plant stress. Vegetation becomes Seasonal Tropical Rainforest and has a distinct season for |

| | |flowering and fruiting. |

|Vegetation → Climate: |Vege - Evergreen Tropical |Evapotranspiration leads to convectional rainfall, recycling some of the water necessary for plant growth. When the vegetation (forest |

| |Rainforest |cover) is removed, there is less rainfall in that area as a result. |

| | | |

| |Climate – Convectional Rainfall| |

|Climate → Relief |Climate – Orographic rainfall |In areas of high rainfall (orographic type) and high relief, rates of erosion are greater. This leads to a change in the shape of the |

| | |land: landslides, riverbank erosion, and deposition on Varzea. |

| |Relief – Andes foothills etc. | |

|Relief → Climate |Relief – Andes and Coastal Mtns|Orographic rainfall in Brazil’s coastal mountains and further west in the Andes foothills affects local climate and on a broader scale provides more |

| | |rainfall from the Amazon Basin. Areas immediately to the west of the coastal mountains of Brazil are affected by drier air, producing a rain shadow as |

| |Climate – Orographic Rainfall |a result. Where rainfall is significantly less and conditions become more drought-like. |

| |and Rain shaodow | |

|Soil → Vegetation |Soil – Vazea soils |An increase in soil nutrients leads to an increase in plant growth. Most Amazon soils are of low fertility except for the alluvial Varzea and soils |

| | |derived from volcanic materials in the Andes foothills. |

| |Vege – Vigorous growth | |

|Vegetation → Soil |Vege – Highly adapted to grow |The system of nutrient recycling in the humus layer means that rainforest vegetation has evolved through time to grow in soils of poor fertility. Where|

| |in conditions |the vegetation has been removed, soils are easily eroded. This has occurred near roads, settlements, farms, HEP dam projects and mine sites. |

| | | |

| |Soil – Humus layer | |

|Relief → Soil |Relief – Terra Firme, Varzea, |There is a dramatic variation in soils found on different relief features. |

| |etc |Terra firma – poor soil, deeply weathered parent material. |

| | |Varzea – good soil, new supply of nutrients each year. |

| |Soils – types Latosols, |Andes soil – Steep land, thin soil. |

| |Andosols, Podzols, alluvial |Ancient lake bed – deeply weathered no nutrients |

| |soils | |

|Relief → Soils |Relief – Terra Firme, Varzea, |On steeper land, erosion is more significant in modifying the landscape. The soils become thinner and less fertile as a result. On flat land and flood |

| |etc |plains, alluvial material is deposited annually by floods onto soils. This increases or maintains their fertility. Soils of the older river terraces |

| | |(terra firme) and the dissected ancient shield areas are of low natural fertility, are well drained and are not eroded due to their location in the |

| |Soils – types Latosols, |already dissected and worn down uplands, resulting in little gain or further loss of plant nutrients as a result. |

| |Andosols, Podzols, alluvial | |

| |soils | |

|Vegetation → Relief | |When vegetation is removed naturally or is bulldozed, burnt, or cut down, the relief can change through increased erosion by water and wind. |

FQ 2 Why do natural landscapes vary from place to place?

A number of processes occur on the Earth’s surface that acts together creating landscapes. These processes act in varying intensities at different locations to produce a range of landscape types.

Geomorphic cycle[pic]

Building processes

• Tectonic processes cause the land surfaces to rise.

• The earth surface is pushed upwards

• Volcanic eruption build land by depositing material

• Earthquakes build land when pressure force blocks upwards

• Pressure from the mantle causes plates to push against each other, buckling the earths surface and causing fold mountains

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Wearing Processes

• Weathering – the force of water and gravity work together to wear down landforms

• Mass wasting – processes that break up rocks so they can be moved. Chemicals, water, wind, ice and other rocks can be responsible

• Erosion – fluvial & Aeolian. Water and wind breaking up and moving material

• Fluvial processes – the movement of water in rivers and streams that carry rocks and other material downstream

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Redistribution Processes

• Generally considered to be part of fluvial activity, redistribution involve the movement of rocks and material from the mountains to the coast

• Depositions – where rivers deposit their rocks and soil to form alluvial plains and river terraces

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Land redistribution processes

Land building processes

Land wearing processes

Relief

Soil

Climate

Vegetation

Elements & Interaction Model

Processes

Cause transformation or change

Decomposition into fertile humus

Forming of acid chemicals

Dissolving of minerals in alluvial material

Breaking down the structure of material into small bits

Inputs

Heat

Water

Alluvium

Dead plants

Animals

Insects

Feedbacks

Nutrients for plants

Water for plants

Losses

Water to rivers

Minerals from alluvium

Outputs

Nutrients of plants

Humus layer

Acid chemicals in soil

Stained water

Fertility of the humus layer is enhanced

Further growth of plants

Litter from vegetation fall to the ground

Litter decays on the forest floor

Humus fertility cycle in the Amazon

Sediment load of the river increases

Rivers flood

Silt and alluvium are deposited as the floods recede

ITCZ brings rain twice a year

Alluvial fertility cycle of the Varzea

Fertility of Varzea topsoil is enhanced

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