Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
Eyjafjallajökull is one of the smaller ice caps of Iceland. It is north of Skógar and west of Mýrdalsjökull. The ice cap covers the caldera of a volcano with a summit elevation of 1,651 metres.
Oceanic trenches are long and narrow depressions of the sea floor. They are the deepest parts of the ocean floor. They are a type of tectonic landforms.Horst is a raised fault block bounded by normal faults. The word Horst in Dutch and German means ‘heap’. It is a raised block of earth’s crust that has been lifted. It is a tectonic landform.
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