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A short class with Sarah and her students. The other ways are under More.
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Today, we are going to discuss one of the fundamental concepts in tidal science: high and low tides. Can anyone tell me what they think a high tide is?
Isn't a high tide when the water level is at its highest?
Exactly! A high tide is indeed when the water level reaches its maximum point. Now, does anyone know what a low tide is?
That's when the water level is at its lowest, right?
Correct! So, the difference between high tide and low tide is called the tidal range. Does anyone know why this is important for hydrographic surveying?
Because it affects how deep the water is?
Yes! Tides can greatly influence depth readings, so we often must correct for tide levels during surveys. Let's remember: High and Low tides affect depth — think of the acronym HLT.
Got it! HLT for my notes!
Great! So now let’s move on to discussing spring tides.
Spring tides are fascinating! Does anyone know when they occur?
They happen during the full and new moon, right?
That's right! When the sun, moon, and Earth align, we have the highest high tides and the lowest low tides. This alignment creates stronger gravitational pull. Can anyone remember what we call the phenomenon when this happens?
It's called spring tides!
Correct! Spring tides occur about twice a month. Remember: Spring = Super high and super low tides! That’s a two-for-one memory aid.
Super high and super low, got it!
Perfect! Now, let’s discuss the other side of tides: neap tides.
Neap tides present a contrast to spring tides. Can anyone explain when neap tides occur?
They occur during the first and third quarters of the moon, right?
Absolutely! During neap tides, the sun and moon are at right angles relative to Earth, leading to lower high tides and higher low tides. Why do you think it's important to differentiate between spring and neap tides in surveys?
Because we need to take the tide levels into account for accurate measurements!
Exactly! Weight that thought — Lower high tides during Neap days. Remember, LN!
I'll jot that down!
Excellent! Now let’s wrap up with the difference between diurnal and semi-diurnal tides.
One last important distinction: diurnal and semi-diurnal tides. Can someone explain what diurnal tides are?
Diurnal tides only have one high tide and one low tide each day.
Right, while semi-diurnal tides have two of each. Does this variability affect hydrographic surveys?
Yes! If you're surveying an area with diurnal tides, you need to plan differently than if it has semi-diurnal tides.
That’s exactly the point! Different patterns require different methodologies. Remember this key sentence: Diurnal = Once, Semi-diurnal = Twice! The acronym DOST will help you.
Meaning diurnal is one time, semi is two times?
Yes! Great job everyone. Let’s summarize what we’ve learned today.
Today, we covered several types of tides: high and low; spring and neap; diurnal and semi-diurnal. Can anyone summarize the key points?
High tides are when water levels are high, and low tides are the opposite. Spring tides are the strongest tides coming every full or new moon, while neap tides are weaker coming every quarter moon.
Diurnal tides are one cycle a day, while semi-diurnal have two cycles!
Excellent recap! Remember these concepts and acronyms to help guide your understanding. Tides play a crucial role in hydrographic surveying and navigation. Well done, everyone!
The highest point of water level in a tidal cycle.
The lowest point of water level in a tidal cycle.
High and low tides occurring during the new and full moon.
Lower high and higher low tides occurring during quarter moon phases.
Tidal pattern of one high and one low tide each day.
Tidal pattern of two high and two low tides each day.
Tides rise high, then they go low, in spring they’ll flow, in neaps they’ll slow.
Imagine a surfer waiting for the perfect wave. During a spring tide, the waves are grand. But when neap comes, the surf is gentler, teaching us how tides influence water levels.
For spring tides, think Super high, and for neap, remember Not so much.
DOST - Diurnal One, Semi-Diurnal Two!
Term
What is a high tide?
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Term
Define spring tide.
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What are neap tides?
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Explain diurnal tides.
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The maximum water level reached at a specific location during the tidal cycle.
The minimum water level reached at a specific location during the tidal cycle.
A tide that occurs when the sun, moon, and Earth are aligned, resulting in the highest and lowest tidal levels.
A tide that occurs when the sun and moon are at right angles relative to the Earth, resulting in lower high tides and higher low tides.
A tidal pattern with one high tide and one low tide each lunar day.
A tidal pattern with two high tides and two low tides each lunar day.
This section describes the various types of tides, including high and low tides, spring and neap tides, as well as diurnal and semi-diurnal tides.
Understanding the different types of tides is important in hydrographic surveying as they impact depth readings and navigation. The section breaks down tides into categories: high and low tides, spring tides, neap tides, and diurnal versus semi-diurnal tides.
Tides are the rise and fall of sea levels caused by the gravitational forces exerted by the moon and the sun. In this section, we explore the four primary types of tides relevant to hydrographic surveying:
High Tide and Low Tide: High tides are the maximum water levels at a given location, while low tides represent the minimum water levels. The difference between these two is called the tidal range.
Spring Tides: These occur when the Earth, the moon, and the sun align. Spring tides result in the highest high tides and the lowest low tides, occurring approximately every two weeks during the full and new moon phases.
Neap Tides: Neap tides occur when the moon is at a right angle to the Earth-sun line, resulting in lower high tides and higher low tides. They happen during the first and third quarters of the moon.
Diurnal and Semi-diurnal Tides:
The significance of understanding these tidal patterns cannot be understated in hydrographic surveying, as they directly affect depth readings and necessitate tide corrections for accurate data collection.