# Tag Info

Accepted

### What is the shortest path between two points on Earth's surface?

If you don't want to do the calculation yourself, you can use an online calculator like the one provided by NOAA. Alternatively, if you do want to do the calculation yourself you can use the ...

### A parcel of air in an isothermal layer

Isothermal, as you are likely aware means constant temperature. Your problem has the givens: The 0 - 1 km layer has a constant temperature of 0 C A surface parcel initially has a temperature of 0.5 C ...

### What is the shortest path between two points on Earth's surface?

45E is directly opposite 135W. It's therefore obvious (hopefully) that the shortest path is straight over the North pole (which is at 90 degrees North). The path takes us round 120 degrees of the ...

### The free oxygen (O$_2$) in the atmosphere is largely a result of what process?

You are correct in thinking that oxygen comes from photosynthesis. In fact it is so much associated with photosynthesis, as opposed to any inorganic process, that the presence of oxygen in the ...
Accepted

### How do I convert between different east longitude coordinates?

The database with the negative longitude angles is storing longitude as eastings and westings, whereas the other database is storing everything as eastings. It appears you prefer your data as ...

### Lake inflow-outflow problem

Everything you did looks reasonable. There is one error in the 'net inflow into lake' line where you take the area of the lake to be $100\cdot10^3\ \text{m}^2$ instead of $100\cdot10^6\ \text{m}^2$, ...
Accepted

### Making clouds for science project

To form a cloud, generally speaking, pressure does not play a significant factor (with the exception of the effect on temperature). If you want to prove that to yourself, go outside when it is foggy ...
Accepted

### The fertility of the soil

From this paper from 1958 (page 2), ... gaseous nitrogen of the atmosphere represents a vast store of potential fertility. It is not directly available to plants. Nitrogen-fixing bacteria, how- ...
Accepted

### Oxygen isotope ratio and Glaciers

It does make sense. As you said - glaciers have lower 18O/16O. This is because they have less 18O overall. Therefore, the oceans have more 18O. But this is today. At the Cretaceous there were no ...

### Help determining virtual geomagnetic pole

You say you're "not given the declination angle", but you also say "the horizontal direction of magnetism of these lavas is due west". That's your declination angle, right there! Since I assume (from ...

### Number of tectonic plates

This is primarily an exercise in interpreting a minimalist diagram. Believe me, you will have to learn to read even sketchier diagrams. That said, the test had the correct answer to the question. ...
Accepted

### Interpreting a geological map

1. What is the youngest/oldest rock in the geological history of this map. Your approach is the right one but isn't the limestone underlain by something? Drawing the AB cross section would be of ...

### Take all the CO2 in the atmosphere and put it into a layer on the surface of earth, how thick would the layer be?

Ok, based on the comments above, this is where I am at... earth's radius is $6371 \text{ km}$ earth is a sphere There is approximately $3 \cdot 10^{15}$ kg of CO2 in earth's atmosphere The density ...

### Plotting a mineral stability diagram

Remember that you are concerned about stability fields. The lines on your stability diagram are the places where two minerals are in equilibrium. One one side one mineral will be more stable, on the ...

### Why is there a seasonal cycle to the amount of CO2 in the atmosphere?

The magnitude of these seasonal variations differ from location to location. The graph below portrays variations in CO2 levels at Point Barrow Alaska (PTB), La Jolla California (LJO), Mauna Loa ...

### Oxygen isotope ratio and Glaciers

There is a quite relevant paper in Science with a fine analysis and interpretation on $\delta$ 18O evolution during the Phanerozoic Eon, which quite summarily display how this ratio depend on the sea ...

### Where are the oldest igneous rocks found?

Zircons from Australia at 4.4Ga, and perhaps basalts from a Canadian island at 4.5Ga. It would interest you to know the quest of Boston University geochemist Matthew Jackson, who is searching for the ...
Accepted

### How can I normalize this chemical analysis to a mineral with 3 cations?

The first step I did was divide each wt% by their molecular weights to get a molecular proportion: Actually that's not what you did. What you did is how much moles of each oxide you have assuming 100 ...

### Maps and Faults

There are no dips given, so you have to work by pure geometric deduction. The sediment subcrops on the east side all seem to be roughly parallel to the contours, which suggests near horizontal ...
Accepted

### A sedimentary rock with only minerals

This is a really bad question, because all three can lack fossils, or all three can have fossils. The definition of "minerals" is also a bit unclear, because fossils are also made out of minerals. I'...

### The fertility of the soil

What does 'nitrogen' mean? Nitrogen might mean gaseous $N_2$. It might also mean compounds, which contain nitrogen, such as nitrate, ammonia and ammonium. $N_2$ $N_2$ cannot be metabolized by most ...
Accepted

### How to graph gravity as a function of depth, given radius and density?

As long as we deal with a spherically symmetric planet, the mass of the shell above you does not influence the observed gravity; the little mass close by exactly cancels the large amounts of mass far ...

### Number of tectonic plates

There are three plates, because there are two plate boundaries (marked in blue): a convergent margin to the left, and a divergent margin to the right. Lithospheric plate #2 contains only oceanic ...

### Interpreting a geological map

From the dips it is obvious that the stratigraphic structure is a syncline, in which case you correctly deduce that the youngest layered rock is the mudstone. But look carefully. The dips on either ...

### How to calculate hydrostatic equilibrium?

I am assuming you are asking for the case of sea level being 200m higher and in isostatic equilibrium. In that case we can make use of Airy's isostasy model: https://en.wikipedia.org/wiki/Isostasy#...

### Why is there a seasonal cycle to the amount of CO2 in the atmosphere?

The respiration of plants is not evenly distributed through seasons since the northern and southern hemisphere have a different amount of land and plants. The southern hemisphere has far less land. ...
Accepted

### Relative dating of intrusion

It does seem like it's impossible to know unless you have additional information. However, I think there is a hint in there. See this white halo around the intrusion? My guess (and I could be wrong ...
Inclination is given by $$I=\arctan(2\cot\theta)$$ where theta is equal to 90° minus the observer's latitude (in the Northern Hemisphere), therefore $$I=\arctan(2\cot(90-40))=59,21^\circ$$ To get ...