Yep, this is the right idea. This is why eating predators like Tuna is worse than eating seafood lower on the food chain.

Yeah, which has nothing to do with covid. Covid never killed the host that quickly, there was never pressure for it to get less dangerous.

[removed]

[removed]

[removed]

We have it easy in the northern hemisphere--Earth is closest to the Sun on January 3, farthest from the Sun in July. The southern hemisphere gets the worst of it in both months (hotter summers and colder winters), though it's mediated somewhat by more ocean in the southern part of the planet.

Mercury is excreted by the kidney, the half-life of methylmercury in the blood is ~70 days

[removed]

I don't actually know how much influence tidal forces have on the Earth's interior temperature. But here are some thoughts to consider.

The Moon very small compared to Earth and much less massive. To get a sense for that, compare the Moon's entire radius (~1740km) to just the radius of Earth's core alone (~3480km). Just our core alone is twice the radius of the whole Moon.

The Moon is made mostly of rock, like our mantle. Rock is very not-dense compared to metal. It's so not dense that the change in density from the deepest part of the mantle to the shallowest part of the outer core is MORE than the change in density from our atmosphere to the crust.

And then our mantle (rock) adds on another 84% of Earth's volume.

So while there is going to be some amount of tidal heating experienced by Earth on account of the Moon, I suspect it's likely not significant. Earth is just SO MUCH more massive than the Moon. (But hey, I could end up being wrong!)

Corals only reflect one method for reconstructing past sea level, and while quite accurate recorders, their use is limited to the last few hundred thousand years (e.g., Woodroffe & Webster, 2014). For a complete answer, we must consider the varied array of methods used to reconstruct sea level over the phanerozoic, e.g., sequence stratigraphic techniques, stable isotopic records, etc.

[removed]

[removed]

[removed]

[removed]

[removed]

[removed]

[removed]

[removed]

It is toxic to everything as far as I’m aware. The major danger of the bio accumulation idea is that the higher up in the food chain an organism is the more it will accumulate those toxins and die. So for example a plankton might have only a few molecules of mercury in it, but then zooplankton eats 20 of those so it has 20x the mercury in it. Then a fish eats 20 of those and so it has 400x the mercury in a plankton. And so if a human eats fish five times a week that human is potentially eating lots of mercury, and that mercury isn’t ever excreted by the body.

If we're talking about sea level reconstructions further back than we have tide records (i.e., direct measurement of average sea level in multiple places globally) or the modern where we primarily rely on satellite altimetry data (e.g., Strassburg et al., 2014), then there are a wide array of methods used to reconstruct sea level. A non exhaustive list:

1. Dating packages of specific types of coral reefs. Particular species of corals can only live within a very narrow range near sea level. If sea level rises, the existing corals will die (from lack of light) and the colony will move upward building on top of the old corals. If sea level lowers, the existing corals will die (from exposure) and the colony will move downward and build on the flanks of the old corals. If you then date the different packages of corals you have a relative sea level record. To make this an absolute record of sea level, you need to know something about the rate of rock uplift of the area to which the corals are rooted. Dating of packages of corals that are now completely above sea level along tectonically active coast lines, like Papua New Guinea, can be used to construct sea level curves if the rate of rock uplift can be constrained through a variety of other means (e.g., extrapolation of geodetic rates, low temperature thermochronology, etc). There are varieties of studies that estimate portions of the sea level curve through these means (e.g., Cutler et al., 2003, Chappell, 2002).

2. Backstripping sediment records. Basically looking at the stratigraphic records of sedimentary basins and using the record of subsidence (after accounting for sediment compaction and subsidence driven by tectonics) to work out the relative height of different packages which are tied to different sedimentary environments that may be relevant for sea level (e.g., Sahagian et al., 1996, Kominz, 1995, Levy & Christie-Blick, 1991, etc.)

3. Sequence stratigraphy as interpreted from seismic records. This is a methodology really pioneered by the oil industry using large 2D and 3D seismic sections of marine. These rely on identifying packages (sequences) and finding the geometric relations between their boundaries, i.e., onlap, offlap, etc., which provide indications of relative sea level through time (e.g., Christie-Blick, 1991). These techniques have been used to produce large-scale global estimates of sea level (e.g., Vail et al., 1977, Haq et al., 1987, Haq & Al-Qahtani, 2005).

4. Similar to the prior one, sequence stratigraphy applied to continental sedimentary records as opposed to seismic stratigraphy (e.g., Sloss, 1963, Ronov, 1994, Haq & Schutter, 2008 etc.)

5. Proxy records for ocean temperature and ice sheet volume. Specifically, marine oxygen isotope records (i.e., primarily the ratio of two stable isotopes of oxygen, ^(16)O and ^(18)O) preserved in a variety of ways (e.g., in the shells of marine microrganisms) are sensitive to the global volume of ice stored on land because during periods where large ice sheets are building, the ice becomes preferentially enriched in light ^(16)O whereas the oceans become enriched in heavy ^(18)O (e.g., this explainer from NASA). Thus reconstructing this ratio within the ocean as preserved in marine organism shells (where the age of these organisms are known through dating the sediment within which they are deposited) allows us to reconstruct the relative volume of ice and thus the sea level (along with associated data on temperature, etc). There lots of studies building out parts of the global sea level record using multiple independent oxygen isotope records, models, and a variety of other data (e.g., Waelbrock et al., 2002, Siddall et al., 2003, Miller et al., 2011, Grant et al., 2012, Rohling et al., 2014, De Boer et al., 2017, etc.).

6. Recently, new methods have been proposed such as using paleogeographic reconstructions (which themselves represent huge syntheses of stratigraphic, paleomangetic, and paleontological data) to construct sea level curves (e.g., Marcilly et al., 2022).

7. Combinations of portions of above. Many of the above references in fact already combine more than one type of record or proxy to reconstruct a portion of sea level variations. Additionally, there are a variety of efforts to combine as many records as possible to identify disagreements and similarities in these records and to produce as accurate composites as possible (e.g., Miller et al., 2005, Miller et al., 2020).

In summary, if you browse through many of these, you'll see that there are ranges of uncertainty and sets of assumptions for any individual method and the methods do not always agree in detail for specific time periods. However, broadly when comparing the sea level curves derived from different approaches (and using them to refine each other), we find a good amount of coherence and agreement. Thus, while the absolute magnitude of past sea level as estimated from these approaches is likely not completely correct, we have high confidence in the broad patterns and order of magnitude values.

[removed]

[removed]

[removed]

There’s a lot of ways we can figure out ancient sea level. There’s three main ways and they are so the sized together to try and get a complete picture. two methods both come from ocean sediment cores. Using sediment codes you can do two things. Depending on the kind of sediment you find and how old it is, you can reconstruct ancient shorelines. There are usually big sediment deposits that get left behind when sea level dramatically shifts up or down, and these are nice indicators of an ancient shoreline. Sediment cores can also be used to estimate global sea level using oxygen isotopes. Oxygen isotopes fractionate due to natural processes in the water cycle, so depending on the ratio of oxygen 18 to 16, we can take a guess at how much ice was on the land surface. Since we assume the global amount of water is somewhat constant, if we know how much is locked up on land then we can calculate how much must have filled those ocean. Combined with geological models of ancient continent shapes you can arrive at a global sea level. You can also use biostratigraphy like u/agate_ said. Corals are great for this because they live in colonies that can be tens of thousands of years old, so they allow us to see for slight changes in depth and ocean chemistry in the relatively recent past.

Also no denying historic sea level is not equivalent to a flat earther. The major reason to me is that whenever we talk about the past in science we have to put huge asterisks next to everything. We can’t ever really be certain something that happened thousands to millions of years ago happened as we think it did. However we can observe the earth as it is right now, and thus that it isn’t flat.

[removed]