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Actividad

Measuring the depth of seas and oceans: How is it done?

Personajes:

Tema: Plate tectonics

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Competencia Matemática, en ciencia, tecnología e ingeniería

Competencia Ciudadana

Materias y cursos por Sistema Educativo

España > Biología y Geología > 4º ESO > Geología

Enunciado

Observaciones y contexto

In 1940, the geology department of the University of Michigan in the USA allowed women to access the department for the first time. Marie Tharp was one of the first women to enter, graduating in 1945. At the same time, Rosalind Franklin, the chemist who would later be one of the discoverers of DNA, was attending classes at Cambridge University and passing exams with flying colours, but she was unable to graduate or take part in the graduation ceremony because she was a woman. These examples show the difficult world in which women scientists had to work in at the time.

Descripción

Students can:

• calculate ocean depth from the round trip time of sound waves

• draw a graph of depths across the Pacific Ocean

• describe the characteristics of their depth profile

• relate this profile to the plate tectonics theory

Echosonars were first used in the 1920s to measure the depth of the sea and to detect other ships or obstacles. They send a sound wave to the bottom of the sea and count the time it takes for the “ping” to return. This time can be used to calculate the depth if the speed of sound in water is known.

The speed of sound in seawater varies between 1450 ms-1 and 1570 ms-1, depending on salinity, temperature and pressure, but we use 1500 ms-1 for the calculations.

Remember that "t" is the time it takes for the wave to travel to and from the ocean floor. We will have to divide by 2 to calculate the depth of the ocean.

Speed (s) = Distance(d) / Time (t)

Thus the Distance (Depth) = s·t

But remember that "t" is the time it takes for the wave to go to the ocean floor and return, so we have to divide the value by 2.

Sea depth (d) = s·t / 2

This activity is a summary of the activities proposed in:

https://www.earthlearningidea.com/Indices/contents_Spanish.html 

https://www.earthlearningidea.com/PDF/352_Spanish.pdf

Very interesting and simple!

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