Which tide occurs at two-week intervals and involves a maximum difference between high and low tides?

Which tide occurs at two-week intervals and involves a maximum difference between high and low tides?

• A. Spring Tide
• B. Slack Water
• C. Perigee
• D. Semidiurnal Tide

Answer: (A)

Tides at their largest difference between high and low water come from the Sun and Moon pulling in the same direction on Earth. When the Sun, Moon, and Earth line up during new moon and full moon phases, their gravitational forces reinforce each other, amplifying the bulges in the oceans. This creates a spring tide, with the highest high tides and the lowest low tides, so the tidal range is maximum. These alignment events happen roughly every two weeks in the lunar cycle, which is why the interval is about two weeks. In between, when the Sun and Moon pull at right angles relative to Earth (around quarter moons), the tides are smaller—neap tides—with a reduced range. Other terms don’t describe this pattern: Slack Water is a period of little current, Perigee is just the Moon’s nearest approach to Earth (which can influence tides but isn’t the name for the tide type), and Semidiurnal describes a daily pattern of two high and two low tides rather than a two-week cycle of maximum range.

Tides at their largest difference between high and low water come from the Sun and Moon pulling in the same direction on Earth. When the Sun, Moon, and Earth line up during new moon and full moon phases, their gravitational forces reinforce each other, amplifying the bulges in the oceans. This creates a spring tide, with the highest high tides and the lowest low tides, so the tidal range is maximum. These alignment events happen roughly every two weeks in the lunar cycle, which is why the interval is about two weeks.

In between, when the Sun and Moon pull at right angles relative to Earth (around quarter moons), the tides are smaller—neap tides—with a reduced range. Other terms don’t describe this pattern: Slack Water is a period of little current, Perigee is just the Moon’s nearest approach to Earth (which can influence tides but isn’t the name for the tide type), and Semidiurnal describes a daily pattern of two high and two low tides rather than a two-week cycle of maximum range.