UNIT 2. RELIEF

WHAT AM I GOING TO LEARN?
1.The Earth’s structure.
2. The Earth’s surface: continents and oceans.
3. Land relief: mountains, valleys, plateaux and plains.
4. Continental waters: rivers, glaciers, groundwaters and lakes.
5. Coastal relief and the ocean floor.
6. Natural hazards: volcanic eruptions and earthquakes.

WHAT DO I HAVE TO STUDY?
●Unit 1 from your book.
● English handouts and worksheets.
● Spanish and English vocabulary (use your glossary book and vocabulary organizer)
●Activities from your book.
● The outline you made.

1. The Earth’s structure.
The Earth’s structure has three layers: the crust, the mantle and the core.

2. The Earth’s surface: continents and oceans.
The lithosphere is composed of the crust and the upper mantle. Lithosphere is divided into large blocks of rock called plates. For millions of years, the plates move slowly, collide, separate and pass over each other. All this movement formed the Earth’s relief.
The continents:
When you observe a photograph of the planet Earth from out space you can see that a small part of its relief is emerged land (continents), but most of it is submerged land because water covers three-quarters of the Earth’s surface.
Also you can see that most of the emerged land is in the northern hemisphere. The continents, from biggest to smallest are: Asia, America, Africa, Antarctica, Europe and Oceania.

The Oceans:
The continents are surrounded by oceans and seas. These contain saltwater, while lakes and rivers normally contain freshwater. In polar regions the water is in the form of ice.
There are five large oceans, connected to each other:
– Pacific: biggest and deepest ocean.
– Atlantic: second largest ocean.
– Indian: located almost entirely in the southern hemisphere.
– Arctic: smaller than the other oceans and located between the northern part of America, Europe and Asia, and the North Pole.
– Southern: surrounds the coast of the Antarctic and, like Arctic Ocean, consists of enormous blocks of ice called icebergs.

3. Land relief: mountains, valleys, plateaux and plains.
When you observe the Earth’s surface you can see a variety of forms like mountains, valleys and plains. These forms are the result of processes that began millions of years ago.
Two kinds of forces formed the relief:
– Internal forces like the movement of plates, volcanic eruptions, plate movements, etc.
– External agents like wind, rain, rivers, groundwater, lakes, ice, seas, oceans and living things.
The Earth’s internal forces created high relief, while external agents causes erosion.

4. Continental waters: rivers, glaciers, groundwater and lakes.
Continental waters are located on the continents and can be freshwater (rivers, glaciers, groundwater and lakes) or saltwater (inland seas).
River
Rivers are created by the accumulation of rainwater, melted snow and ice from mountains and springs.
Rivers flow from high ground along a river bed into the sea, a lake or another river. When one river flows into another, we call it a tributary.
There are three parts or courses of a river:
– Upper course: the source of the river and the first few kilometres of its journey; this is the steep flowing part. In this part, rivers erode valleys into a V-shape.
– Middle course: here the land is not so steep and the river flows more slowly and often meanders.
– Lower course: the final part of the river, which ends at the river mouth.
At the mouth of the river we can find deltas formed from the accumulation of materials on the coast or funnel-shaped estuaries.

Glacier
Is a large mass of ice that forms at the top of mountains and moves like a river. As it moves, it picks up debris. When the ice melts, the debris forms deposits of stone and mud called moraines.
Glaciers erode valleys into a U-shape.
Groundwater
The filtration of water from rain or streams through permeable, porous rock creates groundwater. When a layer of impermeable rock block the water we find a ground deposits called aquifers.
Lake
It is a permanent accumulation of freshwater in a sunken area of land. If it contains saltwater, it is called inland sea.

5. Coastal relief and the ocean floor.
In coastal areas, the action of the sea shapes the relief to form beaches and cliffs.

At the bottom of the ocean, there are also different relief features, just like on the surface of the continents.

6. Natural hazards: volcanic eruptions and earthquake
Some natural phenomena like volcanic eruptions and earthquakes cause huge catastrophes that affect people’s lives.
Movements inside the Earth cause both these phenomena.
Volcanic eruptions
A volcano is an opening in the Earth’s crust. When a volcanic eruption happens, the volcano ejects molten rock (lava), gases, fire, smoke and ash. During an eruption, there are often big explosions, which throw out cinders and pieces of rock.
A volcano consists of the following parts:
– Crater: bowl-shaped hollow at the top of the volcano, caused by volcanic eruptions.
– Volcanic cone: accumulation of rock and lava that the volcano ejected during the eruption.
– Vent (chimney): vertical channel that allows magma to rise to the surface in the crater.

Earthquakes
Earthquakes are tremors or shaking in the Earth’s crust that can cause fissures and movements on the Earth’s surface.
The strength of tremors is called magnitude. We measure the magnitude with an instrument called a seismograph. We create scales with the information that we obtain from the seismograph. One of the most well-known scales in the Richter scale.
Earthquakes at the bottom of the sea cause tsunamis. The seismic waves cause enormous waves in the water.
The different parts of an earthquake are: the epicentre, seismic waves and the focus.

Vocabulary Unit 2

• Alluvial plain: It is a flat, fertile area where the river deposits sediment.
• Archipelago: It is a group of islands.
• Basin: It is natural depression, or low areas of land. Some are below sea level.
• Bay: It is a small gulf.
• Beach: It is a flat coastal area.
• Canyon: It is a deep channel with steep walls.
• Cape: It is a part of the coast which extends into the sea.
• Cliff: They are steep rock formations in high coastal areas.
• Continental Drift: It is a new theory. There was only continent, which broke up millions of years ago. (Pangaea).
• Continental shelf: It is a place near coastlines. These shelves are vast plateaus which reach of 150 metres.
• Continental slope: It is a place to lead down to the deeper part of oceans.
• Core: It is the deepest layer of the Earth. The core is part solid and part liquid.
• Crater: It is the upper of volcano when magma comes out.
• Crust: It is the surface layer of the Earth. It is a thin, solid layer made of rock.
• Delta: It is a triangular area at the mouth of a river.
• Earthquake:It is caused by plate tectonics. When two plates crash, there is a release of energy that makes the ground vibrate. This vibration is an earthquake.
• Erosion: It is the fragmentation and dissolution of rocks, soil and mud, which is transported by wind or water.
• Estuary: It is the part of a river where it meets the sea.
• Fault: They are blocks rise or sink.
• Fluvial erosion: the rivers erode materials, and create deep valleys and canyons.
• Fold: They are created when the Earth’s surface undulates where plates collide.
• Gulf: It is a large area of a sea or ocean partially enclosed by land.
• Island: It is an area of land surrounded by water on all sides.
• Isthmus: It connects a peninsula to a continent.
• Lava: It is magma comes out of a volcano.
• Lower course: It is down part the river.
• Lower mantle: It is the intermediate layer. It has a depth of 700 to 3,000 km.
• Magma: It is molten rock. It is a very hot material that comes out when a volcano is an opening.
• Mantle: It is the intermediate layer of the Earth. This layer is almost 85% of the Earth’s volume.
• Marine Erosion: waves and currents wear away coasts and create cliffs. The water transports the sediment and deposits it. It forms beaches.
• Middle course:It is a middle part the river.
• Mountain: They are high landforms with steep sides.
• Mountain range: It is a group of mountains.
• Ocean Ridge: It is a large mountain range in the ocean floor .
• Ocean Trench: They are large, deep depressions in the ocean floor.
• Peninsula: It is an area of land surrounded by water on all sides except one.
• Pipe: It is a part of volcano through the magma rises.
• Plain: They are low, flat areas of land.
• Plateau: They are large, raised plains.
• Sediment: They are the erosion’s materials which rests on a basin.
• Solution: water dissolves some rocks, such as limestone, producing unusual caves and landscapes.
• Tectonic Plate: They are the different plates the Earth’s crust. It is a theory
• Tsunami: It is an earthquake on the ocean floor.
• Upper course: It is  the high part in  a river.
• Upper mantle: this is a  layer of the Earth that  has a depth of 70 to 700 km. It is below the crust.
• Valley:It is an area of low land between mountains.
• Volcano:It is an opening in the surface of the Earth through which very hot material comes out.
• Waterfall: It is a section of a river where the water falls vertically.