Earth's Grid, Heat Zones & Time Systems

D · Hydrosphere

The hydrosphere is the water sphere — all oceans, seas, rivers, lakes, groundwater, and ice. The lithosphere is rock, the atmosphere is gas, and the biosphere is living things.

C · It increases from $0^\circ$ toward $90^\circ\text{N}$

Latitude is measured from $0^\circ$ at the Equator to $90^\circ$ at the poles. Sailing north from the Equator means latitude rises from $0^\circ$ toward $90^\circ\text{N}$. Latitude never exceeds $90^\circ$.

B · The Tropic of Cancer

The Tropic of Cancer at $23.5^\circ\text{N}$ is the northern limit of direct overhead sun. The Equator is at $0^\circ$, the Arctic Circle at $66.5^\circ\text{N}$, and the Prime Meridian is a line of longitude, not latitude.

B · Magnetosphere

The four spheres are lithosphere, hydrosphere, atmosphere, and biosphere. The magnetosphere is Earth's magnetic field region, not one of the four spheres in this topic.

A · True

$15^\circ$ of longitude corresponds to 1 hour of time difference because Earth rotates $360^\circ$ in 24 hours.

A · 2 hours

Since $15^\circ$ of longitude equals 1 hour, $30^\circ$ equals $30 \div 15 = 2$ hours of time difference.

B · Cool and dry, possibly with fog

Cold currents cool the air above them and reduce its moisture, producing cooler, drier conditions and often fog. This is why some coastal deserts form beside cold currents.

D · Because of the Coriolis effect from Earth's rotation

The Coriolis effect, caused by Earth's rotation, bends moving water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, curving currents into gyres.

D · Delhi

The pair $(28^\circ\text{N},\ 77^\circ\text{E})$ approximately locates Delhi. Sydney is in the southern hemisphere, London is near $0^\circ$ longitude, and Cape Town is in the southern hemisphere.

C · Both A and R are true, and R correctly explains A.

The Torrid Zone is hottest because near the Equator the sun's rays hit almost vertically, concentrating energy over a small area. So R is the correct explanation of A.

D · Latitude lines are parallels; longitude lines are meridians meeting at the poles.

Lines of latitude (parallels) run east–west and never meet. Lines of longitude (meridians) run north–south and converge at the poles.

A · Torrid Zone — most direct sunlight through the year

The Torrid Zone receives the most direct sunlight through the year. The Frigid Zones get slanted sunlight and are coldest, while Temperate Zones have moderate, seasonal sunlight.

B · One day is subtracted

Crossing the Date Line eastward subtracts a day; crossing westward adds a day. This is why a Tokyo-to-San Francisco flight can land on an earlier calendar date than it took off.

C · Because IST is based on $82.5^\circ\text{E}$, which is $82.5 \times 4$ minutes from GMT

IST is based on the meridian $82.5^\circ\text{E}$. Since each degree equals 4 minutes of time, $82.5 \times 4 = 330$ minutes = 5 hours 30 minutes ahead of GMT, giving UTC + 5:30.

C · A warm ocean current flows past the milder city.

At the same latitude, climate differences are often caused by ocean currents. A warm current raises coastal temperatures and adds moisture, giving milder winters — as the Gulf Stream does for NW Europe.

A · Latitude never exceeds $90^\circ$, so $120^\circ$ must be longitude.

Latitude ranges only from $0^\circ$ to $90^\circ$; longitude ranges from $0^\circ$ to $180^\circ$ each way. A value of $120^\circ$ therefore must be a longitude.

D · Sunday, because it subtracts a day when crossing the Date Line

The correct option is Sunday because when the ship crosses the International Date Line heading east, it subtracts a day from the calendar. Thus, leaving Tokyo on Monday results in arriving in San Francisco on the preceding Sunday.