Landforms on the earth

PHYSICAL ENVIRONMENT

CHAPTER 7

THE PHYSICAL ENVIRONMENT

• Made up of various components or things, including:

– Land-landforms, rocks

– Air-weather, climate

– Water- rivers, lakes, oceans

– Living Environment – wildlife, natural vegetation

Landforms & Rocks

• Created and changed by processes beneath and on the Earth’s surface.

• i.e. of Landforms: mountains, volcanoes

• i.e. of rocks limestone, granite

Rivers Lakes and Oceans

• Covers 75% of earth’s surface

• Rivers-streams of water that flow from high ground to low ground

Weather & Climate

• Atmosphere-gaseous environment surrounding earth.

• Weather- the condition of the atmosphere over a short period of time

• Climate- weather conditions over a long period of time.

• Elements of weather: temperature, rainfall, and wind.

Natural Vegetation

• Plants not planted by people and that grow naturally

Interrelationships between the components

• All these are connected to each other

• i.e. Rain affects the plants that grow

• Help us to understand how these components affect our lives.

Prompt

•Do you think it’s important to appreciate the world we live in? Why or why not?

WORKSHEET

WKBOOK PG. 45

Landforms on the Earth

Earth’s Surface

• Is not flat and is shaped in many different sizes and shapes.

• It’s also NOT one solid mass of rock

Earth’s Surface

• Most of the physical features on Earth’s surface are landforms

• Landforms make the shape of the land

• Landforms can be all different shapes and sizes

Earth’s Surface

• Highest point on land -Mt. Everest in Nepal (8850 meters )

• Lowest point on land-Dead Sea in Israel (400 meters deep)

Types of Landforms

Mountain

• Area of high ground usually more than 600m.

• Steep slopes & narrow top or peak

• When formed close together they form a mountain range

Types of Landforms

Hill

• Area of high ground

• usually less than 600 m

• Usually rounded in shape with gentle slopes

Types of Landforms

Valley

• Low area of land between hills or mountains

Types of Landforms

Plain

• Broad, flat, and low area on earth’s surface

Types of Landforms

Plateau

• Raised area of land with a fairly flat, broad top and steep slopes

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Worksheet

Inside Earth

• Earth is made of 3 basic layers

• Core

• Mantle

• Crust

The Core

• At the center of the Earth

• Temperatures can be as high as 5000 degrees Celsius

• Inner core is solid

• Know why?

• Pressure & weight exerted on the core by the outer layers of the Earth

The Mantle

• 2900km thick!

• 80% of earth’s volume

• More than 2000 degrees Celsius

• Upper part is semi-molten or semi-liquid state

The Crust• Outermost layer of earth

• Varies between 6-70km thick

• Made up of many plates

• The plates float on the semi-molten mantel

• The pieces are different sizes & they fit together like a jigsaw puzzle

Internal Forces that Create Landforms

• Crustal movement-the moving plates of earth’s crust

• Plates move very slowly 1-5 cm/year

• Plates may slide, push, or pull apart from each other

• Mountains & volcanoes are formed from the processes within Earth’s surface

Plate Types

Folding

• When two plates collide with each other layers of rock buckle and form folds

• Folding can be barely noticeable or so large mountains form

• These type of mountains are called fold mountains

Fold Mountains

• Himalays in Nepal

• Formed 40-50 million years ago

• Still growing today

• Why?

• Also found in Andes, Alps, and Appalachian mountains

Vulcanicity

• The process through which magma and other materials reach Earth’s surface

• The hot temperatures causes earth’s mantle to melt

• Magma reaches earth’s surface through cracks in the crust

Vulcanicity

• Outpouring of lava is called an eruption

• The build up of pressure caused by gases leads to a volcanic eruption

• Magma may flow out quietly or by violent eruptions

Vulcanicity

• At Earth’s surface lava hardens as the temperature is cooler

• The build up of lava through a single hole can create a cone-shaped volcano

Volcanoes-Basic Structure

• Consists of a vent, pipe, crater and cone

• Vent-opening in earth’s surface

• Pipe-channel allowing magma to rise to the top

• -crater-bowl-shaped opening where ash & lava are released

• Cone-built up by ash and lava released from multiple eruptions

Volcanoes Around the World

• Form around plate boundaries

• A large number are around the Pacific Ocean in an area known as the Pacific Ring of Fire

WHAT ARE THE 3

DIFFERENT TYPES OF

VOLCANOES?

Types of Volcanoes

Active

• Erupts from time to time and likely to erupt again

• i.e. Krakatau - Indonesia

Dormant

• “sleeping volcano”

• Presently inactive but may erupt again

• i.e. Mt. Fuji in Japan

Types of Volcanoes

Extinct

• Scientists consider it unlikely to erupt again.

• i.e. Mt. Kilimanjaro in Tanzania

• We can never be too sure if a volcano is truly extinct

Plateaux

• Formed when a large amount of magma escapes from a long crack and spreads over a large area

• The lava solidifies and after numerous eruptions a plateau forms

• i.e. Columbia Plateau

HOMEWORK: READ 88-91 TEXTBOOK

WORKBOOK PAGES 48-50 & 53-54

Reading Check

• What are 2 risks of living near a volcano?

• What are 2 benefits to living near a volcano?

• What is another name for Mount Merapi?

• What city is Mt Merapi located in?

• What are at least 2 things the local government has done in case of an emergency from Mt. Merapi?

External Forces that Modify Landforms

Weathering

• Process by which rocks are progressively broken down into fragments

• Can be caused:– Changes in temperature

– Action of water

– Action of plants

Large Changes in Temperature- Desert

• Heat causes the surface of the rock to expand during the day and at night

• Inside of rock remains cool

• At night the air cools, temperatures drop & the surface contracts

• This weakens the rocks surface layer

• If water is present the rock will break off in layers

Action of Water

• Rainwater combines with carbon dioxide to form carbonic acid

• Dissolves rocks like limestone

• Over time can form landforms like caves

Action of Freezing Water

• On high mountains melting snow or rain may enter cracks

• At night the water freezes and expands causing rocks to crack

• During the day the ice melts and the process starts over causing rocks to eventually break apart

Plant Growth

• Wind may drop seeds into cracks of rocks

• Seeds grow into plants and forces crack to widen

• Over time the entire rock may fall apart

Erosion

• Process of wearing down surface materials and moving them from one place to another

• Caused mainly by:

– Running water

– Waves

– wind

Action of Running Water

• Water in streams and rivers carry a lot of sediments (small particles like sand, mud, silt)

• The sediments act like sand paper as it flows over rocks and scrapes and wears away at them

• Over time can form canyons

Action of Waves

• Powerful agents of erosion

• The constant breaking of waves against the shore together with the grinding action of sand and stones produces sandy beaches, caves, and cliffs

Action of Wind

• Wind erosion is common in dry areas with few plants to hold the soil or other loose materials in place

• In deserts strong winds can carry large amounts of sand and wear away rock surfaces

• Since sand is heavy wind erosion takes place mainly at the base of rocks

HTTP://WWW.YOUTUBE.COM/WATCH?V=EXS9GFXGIB0

Erosion & Weathering

How Landforms Affect People

• Where they choose to live

• The way people live

• And the type of activity they engage in

Location of Homes

• It’s hard to build on steep slopes

• People prefer plains and valleys

• i.e. Kinta Valley in Perak Malaysia- people built their homes on the flat valley floor

• Tin ores also attracted people to the site

Location of Homes

• Indonesia- people still choose to live near volcanoes despite risk b/c of fertile soil

Human Activities

• People earn living through farming if they live near volcanoes

• People have adapted by cutting terraces into the slopes

• Plains allow people to build homes and other buildings

Human Activities

• Recreational activities like skiing, trekking, and mountain climbing take place on mountains and hills

• Tourists attractions

– Ayers Rock in Australia

TEXTBOOK PAGE 98

EROSION AND WEATHERING ARE USUALLY CAUSED BY NATURAL PROCESSES, BUT HUMAN ACTIVITIES ALSO HAVE A MAJOR IMPACT ON THE AMOUNT OF EROSION THAT OCCURS. CAN YOU THINK OF WAYS THAT PEOPLE MOVE OR ALTER LAND, AND WHY PEOPLE MIGHT WANT TO DO THIS?

What do you think?

HTTP://SCIENCENETLINKS.COM/INTERACTIVES/SHAPEITUP.HTML

Pop Quiz

• What are the 3 types of volcanoes?

• What are the 3 types of plate boundaries?

• In your own words explain folding.

• In your own words explain vulcanicity.