5.3 EQUILIBRIUM THEORY Flashcards
What are the 3 principle assumptions of equilibrium theory?
- the Earth has no continental land masses but is covered by an ocean of uniform depth. However, the presence of land prevents the tidal bulges from directly circumnavigating the globe.
- there is no inertia in the system and oceans respond immediately to the tide generation force - no force required to see that elevation. However, rotation of the Earth on its axis is too rapid for the inertia of the water masses to overcome in sufficient time to establish an immediate equilibrium tide (ocean depth = 20km)
- the Coriolis and friction effects can be neglected. However, water movements induced by tide-generating forces are subject to friction and Coriolis force, which deflects tidal flows to the right in N hemisphere and left in S hemisphere.
What is the length of a solar vs lunar day?
Solar = 24 hours Lunar = 24 hours 50 minutes
^ as earth rotates and the moon rotates about the earth, the moon doesn’t reach the same rotation/alignment after 24 hours as they’re rotating at different speeds.
What is the arrangement of the sun, moon and earth system during Spring tides?
They are in alignment; there is a New moon on the sunwards side of earth and a full moon on the side furthest away from the sun.
Tidal force due to the alignment is at a maximum, as is the tidal range; generates high tides.
What is the arrangement of the sun, moon and earth system during Neap tides?
The sun and moon are separated by 90 degrees, and the solar tidal force cancels out the lunar tidal force.
The tide’s range is at a minimum, generating low tides.
What are the 4 phases of the earth in its orbit around the sun?
Autumnal equinox (sep 23rd), winter solstice (dec 22nd, shortest day), vernal equinox (march 21st ) & summer solstice (june 22nd, longest day).
At equinox, earth is closer to the sun than solstices, so observe much higher tides.
