A tidal cycle of one high tide and one low tide per day.

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Multiple Choice

A tidal cycle of one high tide and one low tide per day.

A single high water and a single low water in each tidal day describes a diurnal tide. In diurnal tides, you have one rise and one fall per lunar day, which lasts about 24 hours 50 minutes because the Moon’s position changes as the Earth rotates. This is different from semi-diurnal tides, where two highs and two lows occur each tidal day (about 12 hours 25 minutes apart), and from mixed tides, where two highs of different heights occur. Slack tide is the brief moment of little or no current between the flood and ebb, not the overall count of tidal events. Neap tide refers to a condition of lower high tides and lower low tides caused by the Sun–Moon geometry, not the number of tides per day. So, the pattern described fits diurnal tide.

A single high water and a single low water in each tidal day describes a diurnal tide. In diurnal tides, you have one rise and one fall per lunar day, which lasts about 24 hours 50 minutes because the Moon’s position changes as the Earth rotates. This is different from semi-diurnal tides, where two highs and two lows occur each tidal day (about 12 hours 25 minutes apart), and from mixed tides, where two highs of different heights occur. Slack tide is the brief moment of little or no current between the flood and ebb, not the overall count of tidal events. Neap tide refers to a condition of lower high tides and lower low tides caused by the Sun–Moon geometry, not the number of tides per day. So, the pattern described fits diurnal tide.

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