The internal processes in the Earth Biology and geology

4º ESO

Escola Virolai

How is the Earth? Is it static?

More seismicity

Why are these countries more

affected by earthquakes and volcano activity?

CONTINENTAL DRIFT

CONTINENTAL DRIFT

Alfred Wegener proposed the hypothesis that the present continents come from the fragmentation of an older supercontinent, which he called Pangea in 1912.

Alfred Wegener (1880-1930)

GEOGRAPHICAL EVIDENCE

GEOLOGICAL EVIDENCE

BIOLOGICAL AND PALEONTOLOGICAL EVIDENCE

PALEOCLIMATIC EVIDENCE

His theory is based on a series of evidences:

GEOGRAPHICAL EVIDENCESome continents like

Africa and South America have complementary

shapes that fit like pieces of a puzzle.

GEOLOGICAL EVIDENCE

There are similarities between the geological formations of the same age in different continents when we approach their limits.

1 432

5 6

7

BIOLOGICAL AND PALEONTOLOGICAL EVIDENCE

The presence of these residual groups or identical

fossils in continents separated by oceans is

difficult to explain without considering the continents

being linked in the past

We can find a lot of fossils of ringless tress in places that today are located at very high latitudes such as northern Europe

PALEOCLIMATIC EVIDENCE

The apparition of glacial deposits in the old continent of Gondwana indicates the position in which

these lands were long ago, much closer to the South Pole.

PALEOMAGNETISM

Igneous rocks contain magnetic minerals that line up with the Earth magnetic field when the rock is formed by the cooling and solidification of magma.

The orientation of these minerals makes it possible for us to determine what their latitude was when they were formed.

TECTONIC PLATES

The theory of plate tectonics was formulated around 1970 by Tuzzo Wilson.

The theory explains the movement of continents that Wegener announced, the expansion of the oceans, the formation and destruction of continental and oceanic crust, the location of large oceanic trenches and the formation of large ridges.

According to this theory, the outermost part of the Earth is constituted by rigid plates that move one from each other. The movement of the plates is explained by convection currents originated in the asthenosphere

TECTONIC PLATES

The lithosphere, formed by the uppermost solid layer of the mantle and the crust, is not homogenous.

• 2 types of crust - Oceanic crust (thin and dense)- Continental crust (thicker and lighter)

The lithosphere is like a puzzle made up of various pieces (tectonic plates) that fit together, floating adrift on an ocean of magma: the asthenosphere.

Two movements of these plates:

• Vertical movements (due to their weight)

• Horizontal movements

The lithosphere is divided in tectonic plates and can contain

• Only oceanic crust (like the Pacific plate)

• Combination of oceanic and continental crust (most cases)

In the interior of the asthenosphere there are magmatic currents. The differences of temperature at different depths cause the movement.

The convection currents caused by the Earth inner heat are responsible for the movement of the tectonic plates

Take a look at the plate boundaries, where the most spectacular geological phenomenae take place.

Geological phenomena

Mountain ranges and island arcs.

Ocean trenches.

Ocean ridges.

The distribution of volcanos and earthquakes.

PLATES BOUNDARIES

A plate is connected with the one next to through a plate boundary, which can be of three types:

• Divergent or constructive boundaries• Convergent or destructive boundaries• Transform boundaries

PLATES BOUNDARIES

A) Divergent or constructive boundaries: surface taken divergent directions; amounting material solidifies becoming new lithosphere. The relief that forms is called mid-ocean ridge.

- Areas with intense seismic and volcanic activity and high thermal flux

- Magma continuously bubbles up from the asthenosphere

- Mid-ocean ridges are the places where oceans grow

Transform faults

B) Convergent or destructive boundaries: the places where the convection currents push one plate against another, making them collide.

Oceanic vs. Oceanic

One is subducted under the other creating a subduction zone.

Causes major volcanic activity that produces an island arc on the subducting zone.

Islands of Japan and New Zealand

Oceanic vs. ContinentalThe oceanic lithosphere is thinner and denser than the continental one. What is formed is a long pericontinental mountain range, like the Andes.

The Andes, the worlds longest continental mountain range, is result of the collision between the Nazca plate and the South American plate.

Continental vs. Continental

Collision orogens.

Himalayan range (Indian and Eurasian plate)

Himalayan range, formed as a consequence of the collision of the Indian continent with the Eurasian plate.

Massive rock folds hint at the powerful forces that created Sichelkamm, a mountain in Switzerland

Nepal's Earthquake

The earthquake occurred due to faulting associated with the Main Himalayan thrust, where the India

plate is slamming into the Eurasia plate to the north.

C) Transform boundaries

Moving in opposite but parallel directions

Transform faults

Intense seismic activity.

The San Andreas fault in California

EARTHQUAKES AND VOLCANOS

Volcanos and earthquakes

These hot spots occur above fixed areas in

the Earth coreThe spots in the core

where the mantle plumes come from are known as hot spots

The Ring of Fire is an area where a large number of earthquakes and volcanic eruptions occur in the basin

of the Pacific Ocean

Earthquakes

The tensions that create the convection currents on the rocks of the lithosphere may reach break.

The fracture produces a vibration of the ground, an earthquake.

They are continuously produced, though most are barely noticeable. But sometimes the movement is so violent that it damaged buildings, bridges ... and large cracks opened in the ground.

Earthquake waves travel out in all directions from a point: the focus, or point of origin.

The point on Earth’s surface directly above the focus: the epicenter.

Earthquake waves move out from the focus in all directions, like a sphere of waves.

Longitudinal/Primary waves: the most quicker waves. By solid and liquid.

Transverse/Secondary waves. More slower. Just by solids

Surface waves R and L: by the terrestre Surface.

SEISMIC WAVES. Waves that propagate through the interior of the Earth transporting energy from earthquakes

P waves

S waves

L and R waves

Scale measurement Earthquakes are classified according to the energy released or as the damage they cause.

Mercalli intensity scale 

Volcanos

Volcanic con: elevation of the ground due to the accumulation of materials that volcano expulse.  

Magma chamber: This is the area with massive collection of magma below the earth’s crust from which magma flows out.It is situated between 10 to 70 km depth.

Main vent: This is the main exit point (opening or outlet) in a weak zone where molten magma is released to the surface.

Crater: After an eruption, the tip or top of the volcano tends to get blown off, leaving a small depression at the top of it.