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Earth and Space - Natural Disasters and Tectonic Plates

Grade 5IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Earth is composed of four distinct layers: the Crust (5−70 km5-70\text{ km} thick), the Mantle, the Outer Core (liquid), and the Inner Core (solid).

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Tectonic plates are large pieces of the Earth's lithosphere that move on the semi-fluid asthenosphere due to thermal convection currents, driven by heat energy ΔQ\Delta Q.

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Convergent boundaries occur when plates move toward each other (A→←BA \rightarrow \leftarrow B), often leading to subduction or the formation of mountain ranges.

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Divergent boundaries occur when plates move away from each other (A←→BA \leftarrow \rightarrow B), allowing magma (rich in compounds like SiO2SiO_2) to rise and form new crust.

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Transform boundaries involve plates sliding past one another (A⇌BA \rightleftharpoons B). Friction at these boundaries causes energy to build up until it is released as an earthquake.

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Natural disasters like Earthquakes are measured using a Seismograph, which records seismic waves. The magnitude is often expressed on the Richter scale, where each whole number increase represents a 1010-fold increase in measured amplitude.

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Tsunamis are giant sea waves caused by underwater tectonic activity that displaces a large volume of H2OH_2O.

📐Formulae

ρ=mV\rho = \frac{m}{V}

v=fλv = f \lambda

P=FAP = \frac{F}{A}

d=v×td = v \times t

💡Examples

Problem 1:

A tectonic plate is measured to be drifting at a constant speed of v=4 cm/yearv = 4\text{ cm/year}. Calculate the total distance dd the plate will move over a period of t=250 yearst = 250\text{ years}.

Solution:

d=4 cm/year×250 years=1000 cmd = 4\text{ cm/year} \times 250\text{ years} = 1000\text{ cm} or 10 m10\text{ m}.

Explanation:

The distance moved by a tectonic plate is the product of its average velocity and the time elapsed, following the formula d=v×td = v \times t.

Problem 2:

A scientist collects a sample of basalt rock from the oceanic crust. The mass of the sample is m=300 gm = 300\text{ g} and its volume is V=100 cm3V = 100\text{ cm}^3. Calculate the density ρ\rho of the rock.

Solution:

ρ=300 g100 cm3=3 g/cm3\rho = \frac{300\text{ g}}{100\text{ cm}^3} = 3\text{ g/cm}^3.

Explanation:

Density is calculated by dividing the mass of the object by its volume. This help scientists understand the composition of different layers of the Earth.

Problem 3:

If an earthquake at a transform boundary releases seismic waves with a frequency of f=2 Hzf = 2\text{ Hz} and a wavelength of λ=1500 m\lambda = 1500\text{ m}, what is the velocity vv of the seismic wave?

Solution:

v=2 Hz×1500 m=3000 m/sv = 2\text{ Hz} \times 1500\text{ m} = 3000\text{ m/s}.

Explanation:

The speed of a seismic wave through the Earth's crust is determined by multiplying its frequency by its wavelength using v=fλv = f \lambda.